Continuous-wave radar system for detecting ferrous and non-ferrous metals in saltwater environments

ABSTRACT

The present invention includes systems and methods for a continuous-wave (CW) radar system for detecting, geolocating, identifying, discriminating between, and mapping ferrous and non-ferrous metals in brackish and saltwater environments. The CW radar system generates multiple extremely low frequency (ELF) electromagnetic waves simultaneously and uses said waves to detect, locate, and classify objects of interest. These objects include all types of ferrous and non-ferrous metals, as well as changing material boundary layers (e.g., soil to water, sand to mud, rock to organic materials, water to air, etc.). The CW radar system is operable to detect objects of interest in near real-time.

CROSS REFERENCES TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION 1.Field of the Invention

The present invention relates to continuous-wave radar systems and morespecifically to detecting ferrous and non-ferrous metals in saltwaterenvironments.

2. Description of the Prior Art

It is generally known in the prior art to provide devices capable ofpropagating electromagnetic waves through bodies of water, includingseawater and brackish water.

Prior art patent documents include the following:

U.S. Patent Pub. No. 2016/0266246 for A system for monitoring a maritimeenvironment by inventor Hjelmstad, field Oct. 23, 2014 and publishedSep. 15, 2016, is directed to a system for monitoring a maritimeenvironment, the system including a plurality of detection devices fordetecting objects in the maritime environment, the detection devicesbeing configured for object detection according to different objectdetection schemes, and a data processing device having a communicationinterface and a processor, wherein the communication interface isconfigured to receive detection signals from the detection devices, andwherein the processor is configured to determine locations of theobjects in the maritime environment upon the basis of the receiveddetection signals within a common coordinate system.

U.S. Patent Pub. No. 2013/0278439 for Communication between a sensor anda processing unit of a metal detector by inventor Stamatescu, et al.,filed Jun. 20, 2013 and published Oct. 24, 2013, is directed to a methodfor improving a performance of a metal detector, including: generating atransmit signal; generating a transmit magnetic field based on thetransmit signal for transmission using a magnetic field transmitter;sending a receive signal based on a receive magnetic field received by amagnetic field receiver to a processing unit of the metal detector;sending a communication signal, including information from a sensor, tothe processing unit; and processing the receive signal with thecommunication signal to produce an indicator output signal indicating apresence of a target under an influence of the transmit magnetic field;wherein one or more characteristics of the communication signal areselected based on the transmit signal to reduce or avoid an interferenceof the communication signal to the receive signal.

U.S. Pat. No. 8,604,986 for Device for propagation of electromagneticwaves through water by inventor Lucas, filed May 14, 2009 and issuedDec. 10, 2013, is directed to an invention concerning a device forpropagating electromagnetic waves through impure water such as seawateror brackish water. The device comprises a body of polar material, forexample pure water, contained in an enclosure, and an antenna arrangedto emit an electromagnetic signal into the polar material. Excitation ofdipoles in the polar material by the electromagnetic signal causes themto re-radiate the signal, which is thereby emitted into and relativelyefficiently propagated through the water in which the device issubmerged. The device offers the possibility of improved underwatercommunication.

U.S. Patent Pub. No. 2018/0267140 for High spatial resolution 3D radarbased on a single sensor by inventor Corcos, et al., filed Mar. 20, 2017and published Sep. 20, 2018, is directed to a novel system that allowsfor 3D radar detection that simultaneously captures the lateral anddepth features of a target is disclosed. This system uses only a singletransceiver, a set of delay-lines, and a passive antenna array, allwithout requiring mechanical rotation. By using the delay lines, a setof beat frequencies corresponding to the target presence can begenerated in continuous wave radar systems. Likewise, in pulsed radarsystems, the delays also allow the system to determine the 3D aspects ofthe target(s). Compared to existing solutions, the invention, inembodiments, allows for the implementation of simple, reliable, andpower efficient 3D radars.

U.S. Patent Pub. No. 2002/0093338 for Method and apparatus fordistinguishing metal objects employing multiple frequency interrogationby inventor Rowan, filed Feb. 11, 2002 and published Jul. 18, 2002, isdirected to a method and apparatus for distinguishing metal objectsemploying multiple frequency interrogation. In one aspect, the methodincludes interrogating a target with at least two frequencies, obtainingrespective response signals for the two frequencies, resolving theresponse signals into at least respective resistive component portions,comparing the magnitudes of at least two of the resistive componentportions, selecting one response signal from among the response signalsbased on the comparison, and characterizing the target with the selectedresponse signal. In other aspects, the method includes obtainingresponse data by interrogating the target at at least two frequencies,normalizing the response data and comparing the normalized responsedata. A signal is provided indicating the extent of any disagreement inthe normalized response data.

U.S. Patent Pub. No. 2014/0012505 for Multiple-component electromagneticprospecting apparatus and method of use thereof by inventor Smith, filedMar. 27, 2012 and published Jan. 9, 2014, is directed to systems andmethods for the detection of conductive bodies using three-componentelectric or magnetic dipole transmitters. The fields from multipletransmitters can be combined to enhance fields at specific locations andin specific orientation. A one- two- or three-component receiver orreceiver array is provided for detecting the secondary field radiated bya conductive body. The data from multiple receivers can be combined toenhance the response at a specific sensing location with a specificorientation. Another method is provided in which a three-componenttransmitter and receiver are separated by an arbitrary distance, andwhere the position and orientation of the receiver relative to thetransmitter are calculated, allowing the response of a highly conductivebody to be detected.

U.S. Pat. No. 10,101,438 for Noise mitigation in radar systems byinventor Subburaj, et al., filed Apr. 15, 2015 and issued Oct. 16, 2018,is directed to a noise-mitigated continuous-wave frequency-modulatedradar including, for example, a transmitter for generating a radarsignal, a receiver for receiving a reflected radar signal and comprisinga mixer for generating a baseband signal in response to the receivedradar signal and in response to a local oscillator (LO) signal, and asignal shifter coupled to at least one of the transmitter, LO input ofthe mixer in the receiver and the baseband signal generated by themixer. The impact of amplitude noise or phase noise associated withinterferers, namely, for example, strong reflections from nearbyobjects, and electromagnetic coupling from transmit antenna to receiveantenna, on the detection of other surrounding objects is reduced byconfiguring the signal shifter in response to an interferer frequencyand phase offset.

U.S. Pat. No. 7,755,360 for Portable locator system with jammingreduction by inventor Martin, filed Apr. 21, 2008 and issued Jul. 13,2010, is directed to a portable self-standing electromagnetic (EM) fieldsensing locator system with attachments for finding and mapping buriedobjects such as utilities and with intuitive graphical user interface(GUI) displays. Accessories include a ground penetrating radar (GPR)system with a rotating Tx/Rx antenna assembly, a leak detection system,a multi-probe voltage mapping system, a man-portable laser-range findersystem with embedded dipole beacon and other detachable accessory sensorsystems are accepted for attachment to the locator system forsimultaneous operation in cooperation with the basic locator system. Theintegration of the locator system with one or more additional devices,such as fault-finding, geophones and conductance sensors, facilitatesthe rapid detection and localization of many different types of buriedobjects.

U.S. Pat. No. 8,237,560 for Real-time rectangular-wave transmittingmetal detector platform with user selectable transmission and receptionproperties by inventor Candy, filed Oct. 11, 2011 and issued Aug. 7,2012, is directed to a highly flexible real-time metal detector platformwhich has a detection capability for different targets and applications,where the operator is able to alter synchronous demodulationmultiplication functions to select different types or mixtures ofdifferent types to be applied to different synchronous demodulators, andalso different waveforms of the said synchronous demodulationmultiplication functions; examples of the different types beingtime-domain, square-wave, sine-wave or receive signal weightedsynchronous demodulation multiplication functions. The operator canalter the fundamental frequency of the repeating switchedrectangular-wave voltage sequence, and an operator may alter thewaveform of the repeating switched rectangular-wave voltage sequence andcorresponding synchronous demodulation multiplication functions.

U.S. Patent Pub. No. 2005/0212520 for Subsurface electromagneticmeasurements using cross-magnetic dipoles by inventor Homan, et al.,filed Mar. 29, 2004 and published Sep. 29, 2005, is directed to sensorassemblies including transmitter and receiver antennas to respectivelytransmit or receive electromagnetic energy. The sensor assemblies aredisposed in downhole tools adapted for subsurface disposal. The receiveris disposed at a distance less than six inches (15 cm) from thetransmitter on the sensor body. The sensor transmitter or receiverincludes an antenna with its axis tilted with respect to the axis of thedownhole tool. A sensor includes a tri-axial system of antennas. Anothersensor includes a cross-dipole antenna system

U.S. Patent Pub. No. 2017/0307670 for Systems and methods for locatingand/or mapping buried utilities using vehicle-mounted locating devicesby inventor Olsson filed Apr. 25, 2017 and published Oct. 26, 2017, isdirected to systems and methods for locating and/or mapping buriedutilities. In one embodiment, one or more magnetic field sensinglocating devices include antenna node(s) to sense magnetic field signalsemitted from a buried utility and a processing unit to receive thesensed magnetic field signals may be mounted on a vehicle. The receivedmagnetic field signals may be processed in conjunction with sensedvehicle velocity data to determine information associated with locationof the buried utility such as depth and position.

U.S. Patent Pub. No. 2011/0136444 for Transmit and receive antenna byinventor Rhodes, et al., filed Dec. 9, 2009 and published Jan. 9, 2011,is directed to a transmit/receive antenna for transmission and receptionof electromagnetic signals. The transmit/receive antenna comprises a TXsection and an RX section, where the TX section comprises a magneticallycoupled TX element and a TX input terminal and the RX section comprisesat least one magnetically coupled RX element and has an RX outputterminal. Axes of the TX loop element and the at least one magneticallycoupled RX solenoid element are parallel. Moreover, the at least onemagnetically coupled RX element is positioned to provide high isolationat the RX terminal of the antenna from TX electrical signals fed to theTX input. Specifically, the at least one magnetically coupled RX elementis positioned at a so that the net magnetic flux generated by the TXloop element and threading the RX solenoid element is zero.

U.S. Patent Pub. No. 2008/0224704 for Apparatus and method for detectingand identifying ferrous and non-ferrous metals by inventor Westersten,filed Sep. 9, 2005 and published Sep. 18, 2008, is directed to a metaldetector using a linear current ramp followed by an abrupt currenttransition to energize the transmitter coil. The constant emf imposed onthe target during the current ramp permits separation of transientvoltages generated in response to eddy currents in the target and itsenvironment from the voltages arising as a result of an inductiveimbalance of the coil system. The temporal separation of the variousvoltages makes reliable differentiation between ferrous and non-ferroustargets possible.

SUMMARY OF THE INVENTION

The present invention relates to a radar system, and particularly acontinuous-wave (CW) radar system for detecting ferrous and non-ferrousmetals in saltwater environments.

It is an object of this invention to provide a CW radar system fordetecting ferrous and non-ferrous metals in saltwater environments,increasing radar geolocation accuracy, enabling the identification ofthe type of material of a target object, discriminating between ferrousand non-ferrous target objects, and mapping target objects onto a 2D and3D coordinate system.

In one embodiment, the present invention includes a CW radar system fordetecting ferrous and non-ferrous metals in saltwater environments.

In another embodiment, the present invention includes a method for usinga CW radar system to detect ferrous and non-ferrous metals in saltwaterenvironments.

In one embodiment, the present invention includes a CW radar system forgeolocating ferrous and non-ferrous metals in saltwater environments.

In one embodiment, the present invention includes a CW radar system foridentifying ferrous and non-ferrous metal types in saltwaterenvironments.

In one embodiment, the present invention includes a CW radar system fordiscriminating between ferrous and non-ferrous metals in saltwaterenvironments.

In one embodiment, the present invention includes a CW radar system formapping in two dimensions (2D) and three dimensions (3D) ferrous andnon-ferrous metals in saltwater environments.

These and other aspects of the present invention will become apparent tothose skilled in the art after a reading of the following description ofthe preferred embodiment when considered with the drawings, as theysupport the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1A illustrates a block diagram of a continuous-wave (CW) radarsystem according to one embodiment of the present invention.

FIG. 1B illustrates a pipe frame for a CW radar system according toanother embodiment of the present invention.

FIG. 1C illustrates a CW radar system according to yet anotherembodiment of the present invention.

FIG. 1D illustrates the CW radar system of FIG. 1C showing the locationof antennas in the piping according to another embodiment of the presentinvention.

FIG. 1E illustrates a side view of a CW radar system according to oneembodiment of the present invention.

FIG. 1F illustrates a top view of a CW radar system according to oneembodiment of the present invention.

FIG. 1G illustrates a port view of a CW radar system according to oneembodiment of the present invention.

FIG. 1H illustrates a radar corner reflector used during calibration ofthe CW radar system according to one embodiment of the presentinvention.

FIG. 2 illustrates an antenna setup for Transmitter (Tx) and Receiver(Rx) antennas for a CW radar system according to one embodiment of thepresent invention.

FIG. 3A illustrates a cross-polarization orientation for Tx and Rxantennas according to one embodiment of the present invention.

FIG. 3B illustrates a cross-polarization orientation for Tx and Rxantennas according to another embodiment of the present invention.

FIG. 3C illustrates a cross polarization orientation for Tx and Rxantennas according to another embodiment of the present invention.

FIG. 4 illustrates an antenna setup for Tx and Rx antennas for a CWradar system according to one embodiment of the present invention.

FIG. 5 illustrates an antenna setup for Tx and Rx antennas with anindication of return length differences between Rx antennas for a CWradar system according to one embodiment of the present invention.

FIG. 6 illustrates a phase shift between Rx antennas for a CW radarsystem according to one embodiment of the present invention.

FIG. 7A illustrates variances in signal strength between Rx₁ and Rx₂antennas for the Rx₁ antenna according to one embodiment of the presentinvention.

FIG. 7B illustrates variances in signal strength between Rx₁ and Rx₂antennas for the Rx₂ antenna according to one embodiment of the presentinvention.

FIG. 7C illustrates variances in frequency using a lower frequencyaccording to on embodiment of the present invention.

FIG. 7D illustrates variances in frequency using a Tx frequencyaccording to one embodiment of the present invention.

FIG. 7E illustrates variances in frequency when using a higher frequencyaccording to one embodiment of the present invention.

FIG. 8 illustrates object detection ranges for a CW radar systemaccording to one embodiment of the present invention.

FIG. 9 illustrates a precision detector for a CW radar system accordingto one embodiment of the present invention.

FIG. 10 illustrates a graph indicating constructive and destructivezones associated with locating an object in a saltwater environmentaccording to one embodiment of the present invention.

FIG. 11A illustrates a graph indicating constructive and destructivezones created by a boat and a dinghy associated with locating an objectin a saltwater environment according to one embodiment of the presentinvention.

FIG. 11B illustrates a graph indicating the energy product for a CWradar system according to one embodiment of the present invention.

FIG. 11C illustrates a graph indicating antenna signal strengthassociated with constructive and destructive zones of a CW radar systemaccording to one embodiment of the present invention.

FIG. 11D illustrates a graph indicating a fore and aft antenna energyproduct associated with constructive and destructive zones of a CW radarsystem according to one embodiment of the present invention.

FIG. 12A illustrates a three-dimensional (3D) underwater depth mapindicating no objects detected by a CW radar system according to oneembodiment of the present invention.

FIG. 12B illustrates a 3D underwater depth map indicating multipleobjects detected by a CW radar system according to one embodiment of thepresent invention.

FIG. 13A illustrates a 3D underwater depth map indicating the locationof objects according to one embodiment of the present invention.

FIG. 13B lists all of the labels in FIG. 13A representing differentgeographic locations for detected objects according to one embodiment ofthe present invention.

FIG. 14A illustrates a two-dimensional (2D) underwater depth mapindicating location coordinates for a detected object according to oneembodiment of the present invention.

FIG. 14B lists all of the labels in FIG. 14A representing differentgeographic locations for detected objects according to anotherembodiment of the present invention.

FIG. 15A illustrates a 2D underwater depth map indication locationcoordinates for detected objects according to another embodiment of thepresent invention.

FIG. 15B lists all the labels in FIG. 15A representing differentgeographic locations for detected objects according to one embodiment ofthe present invention.

FIG. 16A illustrates a surveying operation with a CW radar systemaccording to one embodiment of the present invention.

FIG. 16B illustrates a surveying operation with a CW radar systemconnected to a towing vessel according to one embodiment of the presentinvention.

FIG. 17A illustrates a 2D underwater heatmap indicating the geolocationof detected objects according to one embodiment of the presentinvention.

FIG. 17B lists all of the labels in FIG. 17A representing differentpriority zones on a 2D underwater heatmap for a CW radar systemaccording to one embodiment of the present invention.

FIG. 18 illustrates a 2D underwater heatmap indicating the geolocationof detected objects according to another embodiment of the presentinvention.

FIG. 19A illustrates a 2D underwater heatmap indicating the geolocationof detected objects according to another embodiment of the presentinvention.

FIG. 19B lists all of the labels in FIG. 19A representing differentpriority zones on a 2D underwater heatmap for a CW radar systemaccording to one embodiment of the present invention.

FIG. 20A illustrates a 2D underwater heatmap indicating a CW radarsystem traveling path and the geolocation of detected objects accordingto another embodiment of the present invention.

FIG. 20B lists all the labels in FIG. 20A representing differentgeographic locations for detected objects according to one embodiment ofthe present invention.

FIG. 21A illustrates a 2D graph indicating a land mass and a travelroute for a CW radar system according to one embodiment of the presentinvention.

FIG. 21B illustrates a 2D heatmap graph indicating a travel route for aCW radar system according to one embodiment of the present invention.

FIG. 22A illustrates a circuit diagram of an amplifier board for a CWradar system according to one embodiment of the present invention.

FIG. 22B illustrates a pin configuration diagram for an amplifier boardfor a CW radar system according to one embodiment of the presentinvention.

FIG. 22C illustrates a pin connection diagram for an amplifier board fora CW radar system according to one embodiment of the present invention.

FIG. 22D illustrates a pin configuration and function diagram for anamplifier board for a CW radar system according to another embodiment ofthe present invention.

FIG. 22E illustrates a pin configuration and function diagram for anamplifier board for a CW radar system according to another embodiment ofthe present invention.

FIG. 22F illustrates a chart depicting the flow of signal through anamplifier board for a CW radar system according to one embodiment of thepresent invention.

FIG. 23 lists a table for a primary gain stage of an amplifier board fora CW radar system according to one embodiment of the present invention.

FIG. 24 lists a table for a secondary gain stage of an amplifier boardfor a CW radar system according to one embodiment of the presentinvention.

FIG. 25 lists a table for Stage One and Stage Two gain settings for anamplifier board for a CW radar system according to one embodiment of thepresent invention.

FIG. 26 lists a table for gain calculations for an amplifier board for aCW radar system according to one embodiment of the present invention.

FIG. 27 lists a table for Stage One and Stage Two gain settings for anamplifier board for a CW radar system according to another embodiment ofthe present invention.

FIG. 28A lists a table for resistance values for an amplifier board fora CW radar system according to one embodiment of the present invention.

FIG. 28B lists a table for additional resistance values for an amplifierboard for a CW radar system according to one embodiment of the presentinvention.

FIG. 28C lists a table for additional resistance values for an amplifierboard for a CW radar system according to one embodiment of the presentinvention.

FIG. 29 illustrates an amplifier board for a CW radar system accordingto another embodiment of the present invention.

FIG. 30 illustrates an amplifier board for a CW radar system accordingto another embodiment of the present invention.

FIG. 31A illustrates the top of an impedance matching board for a CWradar system according to one embodiment of the present invention.

FIG. 31B illustrates the bottom of an impedance matching board for a CWradar system according to one embodiment of the present invention.

FIG. 32 illustrates a graphical user interface (GUI) for displayingobjects detected by a CW radar system according to one embodiment of thepresent invention.

FIG. 33 illustrates a GUI for displaying objects detected by a CW radarsystem according to one embodiment of the present invention.

FIG. 34 illustrates a sonar GUI for a CW radar system according to oneembodiment of the present invention.

FIG. 35 illustrates a travel route GUI for a CW radar system accordingto one embodiment of the present invention.

FIG. 36A illustrates a two-dimensional (2D) map indicating a log scaleof a normalized energy product for a CW radar system with no detectedtargets according to one embodiment of the present invention.

FIG. 36B illustrates a 2D map indicating a log scale of a normalizedenergy product for a CW radar system with detected targets according toanother embodiment of the present invention.

FIG. 37A illustrates a 2D density and intensity map for a CW radarsystem according to one embodiment of the present invention.

FIG. 37B illustrates a 2D density map for a CW radar system according toone embodiment of the present invention.

FIG. 38 illustrates a GUI for displaying energy and frequency dataassociated with a CW radar system according to one embodiment of thepresent invention.

FIG. 39 illustrates a GUI for displaying phase detail and power historydata associated with a CW radar system according to one embodiment ofthe present invention.

FIG. 40 is a schematic diagram of a system of the present invention.

FIG. 41 illustrates an amplifier board for a CW radar system accordingto one embodiment of the present invention.

FIG. 42 illustrates an amplifier board for a CW radar system accordingto another embodiment of the present invention.

FIG. 43 illustrates an amplifier board for a CW radar system accordingto yet another embodiment of the present invention.

FIG. 44 illustrates an amplifier board for a CW radar system accordingto yet another embodiment of the present invention.

FIG. 45 illustrates an amplifier board for a CW radar system accordingto yet another embodiment of the present invention.

FIG. 46 illustrates an amplifier board for a CW radar system accordingto yet another embodiment of the present invention.

DETAILED DESCRIPTION

The present invention is generally directed to a continuous-wave (CW)radar system for detecting ferrous and non-ferrous metals in saltwaterenvironments, as well as methods of using the CW radar system to detectferrous and non-ferrous metals in saltwater environments.

In one embodiment, the present invention includes a CW radar system fordetecting ferrous and non-ferrous metals in saltwater environments.

In another embodiment, the present invention includes a method for usinga CW radar system to detect ferrous and non-ferrous metals in saltwaterenvironments.

None of the prior art discloses the use of extremely-low frequency (ELF)electromagnetic (EM) waves in saltwater to pinpoint and/or locateferrous and non-ferrous metals.

Current underwater detection and surveying technologies make use ofmagnetometers which are only able to measure magnetism in ferrousmaterials, such as iron or steel. Magnetometers are unable to detectnon-ferrous metals such as gold, silver, copper, brass, bronze,aluminum, molybdenum, zinc, or lead. In addition, magnetometers onlydetect the strength, or relative change of the Earth's magnetic field ata particular location, and are strictly passive sensors. Thus,magnetometers only use the natural, surrounding magnetism of an object,relying solely on the Earth's fixed magnetic output as the transmitter(Tx). In such a system, only the magnetometer as the receiver (Rx)portion can be modified or manipulated. Moreover, magnetometers have afixed range based on receiver sensitivity which results in a minimaldetection range for ferrous-only materials.

While sub-bottom sonar, side scanning sonar, dual band metal detectors,ground penetrating radar (GPR), and pulsed-wave (PW) radar techniquesare also available, these detection technologies are subject to faultsand limitations that make their usage in saltwater environmentsimpractical.

Sub-bottom sonar systems are able to penetrate the ocean floor, butcannot identify, locate, or differentiate between sedimentary material,ferrous material, and non-ferrous material. These systems can onlydetect “acoustic” impedance, which provides for determining changes indensity from one stratigraphic layer to another stratigraphic layer ofthe subsurface geology. Acoustic impedance corresponds to a physical“pressure” wave (e.g., sound, physical vibrations, earthquakes, etc.),while “electrical” impedance corresponds to an electromagnetic wave(e.g., signals from radio, cell phones, microwaves, light, etc.).Typically, sub-bottom sonar systems operate in the acoustic range of5-50 kilohertz (kHz). While lower frequencies penetrate deeper into mudand silt, these systems lack the ability to provide real detail of thedetected layers. In contrast, higher frequencies provide minor surfacelayer detail, but lack the ability to penetrate sand, mud, or silt.

Side-scanning sonar is typically used to create a map of the oceanbottom. However, much like sub-bottom sonar, side-scanning sonar lacksthe ability to penetrate into the surface of the ocean bottom. Thedevices utilized for side-scanning sonar are also acoustic-only devices.

Dual band metal detectors are also used in underwater salvaging. Thesesystems are active systems and are able to identify ferrous andnon-ferrous metals using dual frequency differences to determine metaltypes (i.e., ferrous vs. non-ferrous). Dual band metal detectors operatein the 5-100 kilohertz (kHz) range and are typically able to penetratebetween 3 inches to 18 inches of sand, saltwater, soil, etc. Inaddition, dual band metal detectors are restricted to searching an areadirectly under the detector unit's coil diameter, which is typicallyless than 12 inches in diameter.

Ground penetrating radar (GPR) systems are used only in airenvironments. The frequency of GPR falls between 10-3000 megahertz(MHz). Even if a GPR system was encapsulated for ocean use, the radarenergy would immediately be absorbed on contact with saltwater and itseffective range would be less than an inch. High frequency, commercial,hand-held metal detectors used on the land have the ability to not onlydetect metal objects (typically <6 ft away), but are also able toclassify what type of metal the object is made of (i.e., gold, silver,iron, etc.). This is accomplished through the differences between themultiple radar bands. In multiple signal systems, signals reflect off ofthe metal, but based on the metal material, the strength and phase ofreturn between the frequencies is different. However, the frequencies ofthese commercial metal detectors do not transmit far enough in saltwaterenvironments before being completely absorbed by the water and hence areoperationally ineffective.

Pulsed-wave (PW) radar systems transmit electromagnetic (EM) wavesduring a time duration, or pulse width. During this process, thereceiver is isolated from the antenna in order to protect the receiver'ssensitive components from a transmitter's high-power EM waves. Noreceived signals can be detected during this time.

The faults and limitations of the previously mentioned detection andsensor technologies have led to the present invention: a continuous-wave(CW) radar system for detecting ferrous and non-ferrous objects insaltwater environments. Such a radar system combines all of the positiveattributes of current sensor and detection technologies with none of thelimitations or faults. Instead of relying on “acoustic” waves, thesystem uses “electromagnetic” waves, but at frequencies which allow forgreater penetration than even the most sophisticated sub-bottom sonarsystems.

The CW radar system generates ELF electromagnetic (EM) waves and usesthose waves to perform functions including, but not limited to,detection, location, and classification of objects of interest. Suchobjects include, but are not limited to, all types of ferrous andnon-ferrous metals, as well as changing material boundary layers (e.g.,soil to water, sand to mud, rock to organic materials, etc.). In oneembodiment, the ELF waves used are between 100 Hz and 3000 Hz. The CWradar system is operable to detect and record all frequencies belowapproximately 3000 Hz. Thus, the ELF waves are operable to propagatethrough water, soil, sand, rock, and/or metals. A portion of the ELFwaves are reflected off of thicker metals and boundary layers, which areused to perform functions including, but not limited to, detection,location, analysis, mapping, and/or classification of objects. Thisentire process is performed using short, manageable antennas which areoperable to transmit and receive the same ELF waves or signals. Thus,the present invention is operable to identify both ferrous andnon-ferrous metals.

In one embodiment, the CW radar system of the present invention makesuse of a multi-band system capable of operating at simultaneousfrequencies in order to decrease location error and provide the abilityto specifically identify the type of metal associated with an objectand/or target during operations.

A key element of this system is the environment it functions in:saltwater. Saltwater is conductive and distributed equally around thesystem's sensors. The saltwater becomes a barrier to transmission, dueto absorption, but simultaneously acts as a filter to keep the detectionranges local to the sensor. Without a saltwater environment, thetransmission ranges measure in kilometers instead of meters. Allconductive surfaces within a few kilometers would create a return signaland greatly reduce the ability to locate a specific target, local to thesensors. Saltwater changes the effective wavelength from potentiallythousands of kilometers to less than 100 meters, enabling detection oftargets, as well as localization of objects around the system's sensorsfrom a few meters to a few hundred meters, based on Tx signal strengthand Rx sensitivity. In one embodiment, the system can handle variationsin salinity within at least a 50 mile radius without further adjustment.In another embodiment, the system can be recalibrated at startup and/orwhen the saltwater environment changes to accommodate different levelsof salinity. In one embodiment, the system is operable to detect targetsand/or objects in brackish water.

The CW radar system is operable to function in deep saltwaterenvironments, from tens of feet to tens of thousands of feet. Moreover,the design of the CW radar system of the present invention preventssaltwater from contaminating the towing device(s) connected to acollecting and/or towing vehicle. The CW radar system is capable ofdetermining absolute object and/or target geolocation to within <4meters (m) circular error probable (CEP) of accuracy. The CW radarsystem is also capable of providing object and/or target geolocationwithin <2 m CEP of accuracy using a relative positioning system. In oneembodiment, relative positioning is determined through the use of arelative GPS receiver. In another embodiment, the relative positioningof detected targets is determined with respect to known metal targets ormarkers placed within the field of search.

Referring now to the drawings in general, the illustrations are for thepurpose of describing one or more preferred embodiments of the inventionand are not intended to limit the invention thereto.

The continuous-wave (CW) radar system of the present invention utilizesa combination of transmitter (Tx) and receiver (Rx) antennas. By usingmultiple Rx antennas, the system is able to localize objects.

FIG. 1A illustrates a block diagram of a continuous-wave (CW) radarsystem according to one embodiment of the present invention. Thecomponents include, but are not limited to, a transmitter computer, areceiver computer, at least two amplifiers, a storage component, atleast two impedance matching hardware components coupled to the at leasttwo amplifiers, a continuous wave sensor head (the submerged, towedstructure comprising the Transmitter (Tx), Receiver (Rx) antennas, downplane, horizontal stabilizer, floatation elements, and structuralsupport elements), a tow point, a Tx communications cable, a Rxcommunications cable. The continuous wave sensor head is comprised of atleast one transmitter (Tx) antenna and at least two receiver (Rx)antennas. The submersion of the Tx and Rx antennas in a saltwaterenvironment modifies the relative Tx and Rx wavelengths from thousandsof kilometers to less than a few hundred of meters range. This enablesthe use of electrically short dipole antennas to collect enough energy,at the Rx antennas, to detect, locate, and/or identify all types offerrous and non-ferrous metals.

FIG. 1B illustrates a pipe frame for a CW radar system according toanother embodiment of the present invention. The CW radar system iscomprised of a multitude of piping, operable to house at least one Txantenna and at least two Rx antennas.

FIG. 1C illustrates a CW radar system according to yet anotherembodiment of the present invention. The CW radar system is comprised ofcomponents including, but not limited to, a tow point, a Rx/Txcommunications cable, a down plane, a horizontal stabilizer, at leastone Tx antenna, and/or at least two Rx antennas. The tow point ispositioned to maximize the stability of the CW radar system while it isbeing towed from a towing vessel. In one embodiment, the towing vesselis a watercraft, including but not limited to a boat, ship, Jet Ski, orsubmarine. In another embodiment, the towing vessel is an underwaterRemotely Operated Vehicle (ROV). In another embodiment, the towingvessel is an Unmanned Underwater Vehicle (UUC). The tow point also helpskeep the tow cable separate from the data cable. The data cable entersthe CW radar system above and behind the tow point on top of the CWradar system. The data cable has multiple electrically shielded wiresrunning throughout the structure to each of the six antennas, four Rxantennas and two Tx antennas. Furthermore, the path of the data cablethroughout the CW radar system is also important, as the cable(s) arerun in order to maximize their individual cross polarization to the Txantennas. By positioning the Tx antennas at a 90-degree angle inrelation to the Rx antennas, this prevents the Rx antenna's wiring fromcoming into contact with the Tx antenna output pattern, further reducingthe crosstalk from the Tx antennas into the Rx antenna data cable(s).The 90-degree angle between Tx and Rx antennas also provides for themajority of the direct path attenuation through the use of thepolarization properties of dipole antennas. Without this attenuation,signal from the Tx antenna would saturate the Rx antenna and anyreturning signal from a target would be lost due to the much, muchstronger direct path signal.

FIG. 1D illustrates the CW radar system of FIG. 1C showing the locationof antennas in the piping according to another embodiment of the presentinvention. The CW radar system is comprised of components including, butnot limited to, at least two bow Rx antennas, at least two Tx antennasplaced approximately at the center of the CW radar system, and at leasttwo aft Rx antennas. In one embodiment, the at least two Tx antennas arepositioned near a horizontal stabilizer for the CW radar system. In oneembodiment, the Tx and Rx antennas are dipole antennas. When two dipoleantennas are placed in close proximity to one another, this sets up atransformer-like condition, resulting in a loss of power to the radarsystem if each antenna is too close to the other. As in a transformer,energy from one Tx antenna is absorbed by any adjacent Tx antenna. Thisresults in a direct loss of usable power and requires the system to alsoprevent this lost energy/power from feeding back in to either Txantenna's circuitry. In order to minimize these effects, the CW radarsystem of the present invention has been constructed with a functionaldistance built into the structure, holding the radar antennas separate.This functional distance is a function of how much transmitted energyloss is acceptable for the CW radar system and the specific transmittedfrequencies being used. In one embodiment, the range for acceptableenergy loss is between 5-20%. In one embodiment, the antennas are placedbetween approximately 9-24 inches away from each other to maintainacceptable energy loss wherein the distance is inversely proportional tothe amount of energy loss. Where the Rx antennas are also dipoleantennas, the Tx antennas must be angled 90-degrees or near-90-degreeswith respect to the Rx antennas in order to maximize the benefits ofcross polarization. In another embodiment, the Tx and Rx antennas areshort dipole antennas. In another embodiment, the Tx and Rx antennas arehalf-wave dipole antennas. In another embodiment, the Tx and Rx antennasare folded dipole antennas. In yet another embodiment, the Tx and Rxantennas are bow-tie dipole antennas. In yet another embodiment, the Txand Rx antennas are cage dipole antennas. In yet another embodiment, theTx and Rx antennas are halo dipole antennas. In yet another embodiment,the Tx and Rx antennas are turnstile dipole antennas. In yet anotherembodiment, the Tx and Rx antennas are sloper dipole antennas. In yetanother embodiment, the Tx and Rx antennas are inverted “V” dipoleantennas. In yet another embodiment, the Tx and Rx antennas are GSRVdipole antennas. In yet another embodiment, the Tx and Rx antennas arenot dipole antennas.

In one embodiment, a Tx antenna is placed in one of two center pipes andthe corresponding Rx antenna pair(s) are perpendicular to the Txantenna, forward and aft. Each Rx antenna is placed approximately 1-3meters from the Tx antenna. The Rx antenna pair(s) are alwaysperpendicular or substantially perpendicular to the Tx antenna in orderto take advantage of the noise cancellation provided by the polarizationcharacteristics of the antennas. In one embodiment, one Tx antennaeffectively has four Rx antennas, two forward and two aft, with each Rxantenna spaced approximately 1-2 meters away from the Tx antenna. In oneembodiment, the Tx and Rx antennas are spaced approximately 60 inchesapart from each other. In one embodiment, the Tx and Rx antennastructures are approximately 14.5 feet in total when using a multibandsystem.

The addition of multiple Rx antennas facilitates the detection of signalstrength and phase changes between the Rx antennas. Each Rx antennaremains perpendicular or substantially perpendicular to the surface ofthe water, while the Tx antenna(s) remain parallel or substantiallyparallel to the water's surface. This keeps the Tx and Rx antennas atright angles to each other, preventing self-jamming and shielding the Rxantennas from the water's surface reflection. Thus, this orientationfunctions to prevent self-jamming and reduce the surface bounce energyfrom the Tx into the Rx antenna(s).

In one embodiment, the CW radar system includes a third Tx/Rx antennacombination. In another embodiment, the CW radar system includes afourth Tx/Rx antenna combination. In yet another embodiment, the CWradar system includes more than four Tx/Rx antenna combinations. In oneembodiment, additional cross pipes are included in the design of thepiping frame, thereby providing for the CW radar system to accommodatemore bands while only increasing the overall length of the piping frameof the CW radar system for each added band. All portions/elements of theunderwater structure housing the cables, Tx/Rx antennas, and connectorsare made from dielectric or non-metallic, non-conducting material.

The entire CW radar system is towed from a single tow point, maximizingstability while towing and keeping the towing cable separate from a datacable. The data cable enters the CW radar system above and behind thetow point. The data cable has multiple electrically shielded wiresrunning throughout the structure to each of the Tx and Rx antennas. Datacables are positioned to maximize their individual cross-polarizationwhile avoiding exposure to the Tx antenna(s) output pattern, reducingcrosstalk from the Tx and Rx antenna data cables.

The structure of the CW radar system of the present invention furtherminimizes issues with vibration. Mechanical vibrations induce a dopplerresponse into the processed data, directly contributing to loss ofSignal to Noise Ratio (SNR) in the system. In one embodiment, theballast between the panels is constructed of high-density foam with acrush depth of more than 4000 feet deep. This enables the system toremain buoyant and keeps panels of the system from vibrating undertowing conditions. The panels also serve to keep the pipes andstructures holding the cables and antennas rigid. Thus, the combinationof the panels and high-density foam reduces overall system vibrationwhen being towed. In embodiment, the system is towed at speeds up toapproximately 12 knots (kts). In another embodiment, the system is towedat a speed greater than 12 kts.

FIG. 1E illustrates a side view of a CW radar system according to oneembodiment of the present invention. A tow point is positioned at oneend of the CW radar system, enabling a towing vessel to attach to the CWradar system. The CW radar system also includes a buoyancy tank,enabling the CW radar system to remain afloat on the surface of a bodyof water. In one embodiment, the CW radar system is connected to thetowing vessel via a tow cable and a data cable. In one embodiment, theCW radar system is connected to the towing vessel via a dinghy, wherethe dinghy is connected to the towing vessel via a data cable and towcable, and the dinghy connects to the CW radar system using the datacable and/or tow cable.

FIG. 1F illustrates a top view of a CW radar system according to oneembodiment of the present invention. The CW radar system includes atleast one down plane, operable to adjust the angle of the CW radarsystem as it travels along the surface of a body of water, and at leastone buoyancy tank.

FIG. 1G illustrates a port view of a CW radar system according to oneembodiment of the present invention.

In one embodiment, the CW radar system includes a down plane. The downplane is placed forward of the center of balance of the CW radar system.This positioning, in conjunction with the two point and horizontalstabilizer, provides a balanced, smooth towing operation. The down planeis sized and angled to provide precise underwater depths for the CWradar system when being towed at peak, desired collection speeds. In oneembodiment, the peak towing speed for collection is approximately 2-8kts. The depths of the CW radar system's keel from the ocean surface area function of tow cable length for a set collection speed. In oneembodiment, the down plane is a fiberglass down plane. In oneembodiment, the down plane is made of polyvinyl chloride (PVC). Inanother embodiment, the down plane is made of fiberglass composite. Inanother embodiment, the down plane is made of a non-metallic,non-conducting, dielectric material. In one embodiment, the down planeis actively adjustable. Using an actively adjustable down plane enablesthe CW radar system to operate at greater depths. In another embodiment,the down plane is coupled with a sonar reflector system on the CW radarsystem in order to precisely locate targets underwater. This coupling ofthe down plane with the sonar reflector system increases thegeolocational accuracy of the CW radar system during surveyingoperations. In one embodiment, the sonar reflector is a corner reflectorthat reflects a sonar acoustic signal. In one embodiment, the sonarreflector signal is used by the towing vessel to determine the locationand depth of the CW radar system as it is being towed. In oneembodiment, the sonar reflector is operable to locate the corners of theCW radar system as it is being towed. In one embodiment, there is atleast one transponder on each side of the towing vessel. Thetransponders each emit signals of different frequencies. The locationand depth of the CW radar system is calculated using the combined stereovision of the at least one transponder on each side of the towingvessel. In one embodiment, the system is operable to generate a 3D imageof the CW radar system as it is being towed with geolocation accuracy ofthe CW radar system within 10 ft.

In one embodiment, the CW radar system of the present invention furtherincludes a towed floatation device attached to the CW radar system. Inone embodiment, the towed flotation device is a dinghy. The towedfloatation device cushions the CW radar system against waves, reducingsudden jerking motions encountered while towing and vibrational noise.In one embodiment, the towed floatation device also carries anadditional GPS receiver that helps to triangulate the location of theunderwater sensor-head during surveying operations. The combination ofall GPS receiver(s) on the towing vessel and the towed floatation devicetogether provide a <1 m accuracy of the underwater sensor-head.

In addition, the overall distance between the CW radar system of thepresent invention and a towing vessel is of critical importance. Theengines, hull structures, electronics, aluminum superstructures, screws,and other vessel or tow components can create a target that is detectedby the CW radar system, even though the parts of the towingvessel/dinghy are above or below the waterline. In one embodiment, theCW radar system is towed from a vessel between approximately 200 feet(ft.) to 500 ft. behind the vessel. In one embodiment, the CW radarsystem is attached to a dinghy, where the distance between the towingvessel and the dinghy is between approximately 100 ft. to 300 ft. andthe distance from the CW radar system and the dinghy is approximately 50ft. to 400 ft. In another embodiment, the dinghy is more than 300 ft.away from the towing vessel and the CW radar system is more than 400 ft.from the dinghy. In one embodiment, the towing vessel is a watercraft(boat, ship, jet ski, submarine, etc.). In one embodiment, the towingvessel is an underwater Remotely Operated Vehicle (ROV). In oneembodiment, the towing vessel is an Unmanned Underwater Vehicle (UUV).In one embodiment, the dinghy is replaced with a dynamic winch systemonboard the towing vessel. The depth of the sensor-head is thendetermined by the distance of the sensor-head behind the towing vessel.The sensor-head distance from the towing vessel is lengthened orshortened to increase or decrease the sensor-head depth.

The CW radar system is capable of transmitting multiple, simultaneousfrequencies, up to approximately 5000 Hz. In one embodiment, the CWradar system is a dual-band system that operates using two separateradars in the same sensor head, enabling the transmission of multiplefrequencies from multiple radars simultaneously. By using multiplefrequencies, the CW radar system has increased 3-Dimensional (3D) targetgeolocation functionality and is operable to more efficiently classifysurveyed objects and/or target materials and detect objects and/ortargets through solid surfaces, the solid surfaces including but notlimited to, soil, sand, reef, mud, and/or iron/steel. In one embodiment,this dual-band system is comprised of at least one Tx antenna and atleast two Rx antennas. In one embodiment, this dual-band system iscomprised of at least two or more Tx antennas and at least two or moreRx antennas. In one embodiment, geolocation is achieved with a set ofglobal positioning system (GPS) coordinates. In one embodiment,geolocation is based on a differential GPS system. In one embodiment,the CW radar system uses GPS receivers on land and/or GPS receivers atanchor points in the underwater environment to improve the accuracy ofthe GPS geolocation using differential GPS. In one embodiment, the CWradar system includes a plurality of GPS receivers located on the towingvessel and on the towed floatation device to improve the accuracy ofgeolocation. In one embodiment, geolocation is based on a localized orrelative coordinate system.

In one embodiment, geolocation is based on a relative coordinate systemwherein the relative coordinate system is defined by metal targetsand/or reflectors placed under or on the water surface and in the surveyfield prior to/or during survey operations. In one embodiment, the metaltargets are aluminum. In one embodiment, the metal targets are roundedso as not to skew the directions of the signals that they reflect. Inone embodiment, the metal targets are used for relative geolocationwithin 1-2 m of a target and/or object. All objects discovered from theCW radar system are then referenced relative to the metal targets and/orreflectors that were placed into the survey field. In one embodiment,geolocation is based on a relative coordinate system using activetransmitters placed under or on the water surface and in the surveyfield prior to/or during survey operations. All objects discovered fromthe CW radar system are then referenced relative to the activetransmitters that were placed into the survey field. In anotherembodiment, the GPS coordinate system is used to locate the metaltargets, active transmitters, and/or reflectors used to define therelative coordinate system. In one embodiment, a combination of GPScoordinates and relative coordinates are used to geolocate the objectsand/or targets in the target survey area.

By using a dual-band system, the CW radar system is able to transmit asignal from any Tx antenna. Additionally, the CW radar system is furtherable to transmit many signals, simultaneously, within a specific band.For example, the CW radar system is able to transmit multiple signalssimultaneously within a frequency band up to approximately 5000 Hz.However, the higher the frequency used, the weaker the overall returnsignal strength is, assuming the same output power per frequency at theTx.

In another example, the transmitter is able to transmit between 0.1 and100+ watts of power. If two frequencies are transmitted from the singletransmitter, each frequency will have one-quarter of the amount of poweravailable. In this system, power is equal to voltage squared. Therefore,in order to transmit two frequencies out of one band, power issacrificed. The CW radar system can generate multiple transmissionfrequencies through one of three methods. In one embodiment, the CWradar system transmits two or more frequencies simultaneously from asingle Tx antenna. This embodiment reduces the number of Tx/Rx pairs inthe overall system, thus reducing the overall physical complexity of thesystem. A single Tx antenna can transmit a few or even tens offrequencies simultaneously. The disadvantage of this approach is thatthe power required to transmit multiple frequencies increases as asquared function of each additional frequency. If one frequency is nowexpanded to two simultaneous frequencies, then the amplifier powerrequired to match the single frequency increases from a factor of (1)²=1to (2)²=4. In the case where the amplifier is at maximum power settingand an additional frequency is added, then signal strength is reducedeffectively from a factor of 1/(1)²=1 to 1/(2)²=¼. In the case of 3simultaneous frequencies, this transmitted power per frequency falls to1/(3)²= 1/9 of the system's total output power.

In another embodiment, there are multiple Tx/Rx pairs in the system. Inone embodiment, there is one Tx/Rx pair for each frequency transmitted.This allows the use of multiple amplifiers (one for each Tx antenna) andprovides more overall power transmitted per each frequency. The currentCW radar in FIG. 1D shows two separate Tx/Rx systems in the samestructure. The structure shown can easily handle 3 or more Tx/Rx pairs.The advantage is that output power can be maximized. A slightdisadvantage is discussed in [00128] above where some power is lost dueto transformer-like losses. The amount of power lost as discussed in[00128] is much less than the amount of power lost in the firstembodiment wherein multiple frequencies are transmitted from a singleTx/Rx pair.

The third embodiment is a combination of approaches 1 and 2 above toachieve the desired number of frequencies transmitted with the desiredamount of power from the total amplifiers in the system. An additionalissue, whether using approach one, two, or three above is that thetransmission of any two frequencies will also generate a third signalwherein the frequency of the third signal is the beat frequency, or thedifference between the frequencies of the two intended signals. As anexample, transmitting two signals at 300 Hz and 500 Hz from eitherapproach above will also generate a third frequency of 200 Hz (500Hz-300 Hz). Transmitting three frequencies will produce the threefrequencies and two additional beat frequencies.

With multiple frequencies being transmitted from a single band radarsystem or a dual band radar system transmitting two distinctfrequencies, the result is that each frequency has its own set ofconstructive and destructive zones that differ in range based on thefrequency (wavelength) of transmission, as illustrated in FIG. 8. Byusing multiple, simultaneous frequencies, the CW radar system isoperable to provide the exact distance to an object and/or target. Asthe distance between the object and/or target and the sensor head of theCW radar system changes, the signals received by the Rx antenna orantennae of the CW radar system transition between constructive anddestructive interference. These transitions depend on the frequency ofthe transmitted signals and are used to measure overall distance betweenthe CW radar system and an object and/or target. The use of multiplefrequencies allows for the CW radar system to detect and identify anobject and/or target with more detail.

In a pulsed system, distance is calculated in part from the time that ittakes for a sent Tx antenna pulse to reach the Rx antenna afterinteracting with an object and/or target. However, with continuous wavesystems, there is no measure of time because the Tx antenna is alwayssending out a signal. The CW radar system of the present inventionsolves this distance measurement issue associated with current CW radarsystems by employing different frequencies with different constructiveand destructive zone lengths, as illustrated in FIG. 8. The combinationof received signals of varying frequencies that have passed throughrespective constructive and/or destructive zones after being reflectedoff an object and/or target allows the CW radar system to preciselyidentify each return signal, as well as the location of an object and/ortarget as well as its composition. The CW radar system also uses thephase shift of the returning signal to compute distance, metal type, andprecise location measurements.

Furthermore, the use of multiple frequencies by the CW radar system ofthe present invention enables the system to detect and/or penetratesteel. In the oil and gas industries, a process known as “Pigging” isused to locate a sensor inside a steel pipe. The sensor transmits afrequency low enough to penetrate a steel walled pipe. The CW radarsystem of the present invention is operable to create these samefrequencies by either directly transmitting a frequency that is lowenough to penetrate a steel-walled pipe or by transmitting two separatefrequencies, wherein the beat frequency of the two separate frequenciesis low enough to penetrate a steel-walled pipe. For example, if the twofrequencies being transmitted from a single radar system areapproximately 311 Hz and approximately 333 Hz, respectively, there is athird signal with a beat frequency also being transmitted at thedifference between the two frequencies. In this example, this beatfrequency is approximately 22 Hz (333 Hz-311 Hz). This third frequencyvalue, 22 Hz, is the typical frequency used in “Pigging.” It transmitsthrough steel and can be detected by the dipole antennas of the CW radarsystem of the present invention.

Cross Polarization

The CW radar system of the present invention uses cross polarization toeliminate the direct path energy from Tx to Rx antennas, which deflectsany reflected energy from an object and/or target. Cross polarizationusing dipole antennas is accomplished through physical orientation. TheTx antenna is oriented 90 degrees from the Rx antenna(s).

FIG. 2 illustrates an antenna setup for Tx and Rx antennas for a CWradar system according to one embodiment of the present invention. TheTx antenna is positioned between two Rx antennas. In addition, the Txantenna is placed at a 90-degree angle in relation to the two Rxantennas.

An added benefit of this embodiment is the noise cancellation providedby the polarization characteristics of the Tx and Rx antennas. Incurrent signals, there are several primary sources of noise. Suddenmovements and/or jerking on any towing device(s) creates significantnoise in the signal received by the Rx antennas, with greater noisecreated in any forward Rx antennas. Another source of noise includesvibration. As the CW radar system moves through water, the turbulenceacross the structure produces a large amount of noise via vibration.Moreover, any flexing of the CW radar system during towing and/orcollecting causes a Doppler effect in the signal(s).

FIG. 3A illustrates a cross-polarization orientation for Transmitter(Tx) and Receiver (Rx) antennas according to one embodiment of thepresent invention. The Tx antenna is placed at a 90-degree angle inrelation to all Rx antennas. In one embodiment, the Tx and Rx dipoleantennas are between approximately 8 to 30 inches in length and havediameters between approximately ½ to 2 inches. In a continuous radarsystem such as the present invention, the direct signal path from the Txto the Rx antenna(s) is of much higher magnitude than that of the returnsignal that has interacted with an object and/or target. Typical radarsystems used by the military and commercial communities use pulsedradar, wherein the Tx antenna sends out short, pulsed bursts of energywhile the Rx antennas are turned off or electrically protected from thedirect path energy to avoid the interference of the direct path energy.The Rx antennas are then turned on when the Tx antennas are turned offin order to receive only the return signal from the object and/ortarget. However, since the frequencies of the present invention areextremely low and the wavelengths of objects are long, pulsed radarsystems will not work in the conditions where the CW radar system of thepresent invention is operable to function. Thus, the CW radar systemuses cross polarization of the Tx and Rx antennas to eliminate thedirect path energy from the Tx antenna(s) to the Rx antennas, enablingthe system to detect distant targets and/or objects while the Rxantennas are located directly next to the bright and loud Tx antenna(s).

FIG. 3B illustrates a cross polarization orientation for Tx and Rxantennas according to another embodiment of the present invention. Crosspolarization using dipole antennas is accomplished through physicalorientation. The Tx antenna is oriented approximately 90 degrees fromthe Rx antennas. When using dipole antennas, multiple Tx antennas inclose proximity to one another result in a transformer-like conditionand loss of power will occur if the Tx antennas are too close to oneanother. In a transformer, energy from one Tx antenna will be absorbedby an adjacent Tx antenna such that none of the transmitted energy willpropagate away from the Tx antenna. The result is a direct loss of powerand a need to prevent this lost power from feeding back into the firstTx antenna's circuitry. In order to minimize these effects, the CW radarsystem of the present invention ensures a functional distance has beenbuilt into the structure holding the separate transmitters. Thisfunctional distance is a function of how much energy loss is acceptableand the specific signal frequencies being transmitted by the CW radarsystem. In one embodiment, the CW radar system of the present inventionseparates Tx antennas by approximately 6 inches to approximately 36inches. Since the Rx antennas are also dipole antennas, the anglebetween the Tx antenna(s) and the Rx antennas is approximately 90degrees, maximizing the benefits of cross-polarization.

FIG. 3C illustrates a cross polarization orientation for Tx and Rxantennas according to another embodiment of the present invention.

FIG. 4 illustrates an antenna setup for Tx and Rx antennas for a CWradar system according to one embodiment of the present invention. TheTx antenna is positioned between two Rx antennas. The Tx antenna isplaced at a 90-degree angle in relation to the two Rx antennas.

In addition, a third source of noise radiates from the electronicequipment powering, controlling, connected to, and/or in close proximityto the CW radar system. All electronics have noise associated with themand must be accounted for and/or corrected for. Included in the noiseradiating from the electronic equipment is the issue of electronicdrift. This electronic drift, or drift current, is caused by particlesgetting pulled by an electric field. Without noise controls,fluctuations in electronic equipment can produce around 30-60 dBW ofsignal, which is equivalent to approximately 1/1,000 of a Watt of signalin the Rx antenna(s). In the presence of an object and/or target, signalin the Rx antenna(s) is in a range of approximately 1/100 of a Watt toless than 1/100,000,000 of a Watt; hence, there is a need to monitor andcontrol noise inputs to the overall system in order to accurately detectsignals in the Rx antenna from an object and/or target.

Drift current, or electronics drift, is caused by electric force, i.e.,charged particles get pushed by an electric field. Electrons, beingnegatively charged, get pushed in the opposite direction of the electricfield, but the resulting conventional current points in the samedirection as the electric field. The CW radar system of the presentinvention must account for drift current from elements including, butnot limited to, temperature, vibrations, and/or system electronics.These elements have a natural drift state. If unaccounted for, excessnoise is created within the system and electronic saturation from thenoise will effectively overpower the target signal strength. Therefore,it is important for the CW radar system to maintain a balancedsignal-to-noise ratio. The CW radar uses multiple elements to reduce orcontrol electronic drift. The first is through DC (Direct Current)biasing control. The second is through Analog Filtering. The third isthrough climate control of the electronic boards/elements duringoperations. The electronic components are mounted in thermal electriccoolers/heaters to maintain constant temperatures during operations.Environmental temperature fluctuations are maintained to less thanapproximately 1° Celsius (C) through a combination of heating andcooling. In one embodiment, the CW radar system is operated at atemperature range of approximately 4° C. to 16° C. to avoid thermaldrift.

Additionally, several sources of signal clutter must be accounted for.These include, but are not limited to, the reflection of the transmittedsignal off the surface of the water above the CW radar system and thereflection of the transmitted signal off the bottom of the ocean.Regarding the reflection off the surface of the water, if the surfacewas perfectly flat, energy from the Tx antenna(s) would be completelyabsorbed at the surface. However, the surface is almost never perfectlyflat due to wave action, ocean swells, wakes caused by other objects,winds, currents, etc., which result in disturbances that create areflection at the air-water boundary, bouncing energy towards the Rxantenna(s). This can amount to approximately 0.00001 to as much asapproximately 0.01 dBW of variance in signal from the surfacereflection. In one embodiment, the signal reflection off the surface ofthe water is most noticeable when the CW radar system is within 150 ftof the surface of the water.

The reflection off the bottom of the ocean is a second source ofclutter, but much less so than the reflection off the surface of theocean. Because sand is typically a mixture of water and rock, theboundary layer effects are minimal. In the case of reef environments, orother rock formations, the boundary layer effects are also minimal, butcan also create noise components that need to be accounted for duringpost-processing.

Phase Shift

When using multiple Rx antennas of differing electrical path lengths inconjunction with continuous wave (CW) transmissions, a phase shiftoccurs in the signals between each Rx antenna. If the path lengths fromthe Tx transmitter antenna to the target and then to the Rx antennas forthe multiple Rx antennas were identical, there would be no phasedifference between the signals received by each antenna. This phaseshift occurs only under a very precise set of conditions, including whenmultiple Rx antennas are placed perpendicular (90 degrees) or nearperpendicular to the direction the system is being towed. In oneembodiment, one transmitter has four receivers, two forward and two aft,with each spaced between approximately 1-3 meters away from the Tx. Inanother embodiment, one transmitter has two receivers, one forward andone aft, with each spaced between approximately 1-3 meters apart.

FIG. 5 illustrates an antenna setup for Tx and Rx antennas with anindication of the return length differences between Rx antennas for a CWradar system according to one embodiment of the present invention. TheTx antenna sends out a signal in search of objects in a saltwaterenvironment. Once detected, the signal is first received by the forwardRx antenna, traversing a first return path length (Rx₁). As the CW radarsystem passes over the detected object, the signal is received by theaft Rx antenna, traversing a second return path length (Rx₂). Becausethe system is a CW transmission and the return path lengths of the twoRx antennas are different, there is a phase difference between thesignals received by the respective Rx antennas. The phase shift is usedto distinguish an object and/or target from background noise andapproximate the distance between the at least one Tx antenna and the atleast one Rx antenna and the object(s) and/or target(s).

In one embodiment, the CW radar system's configuration enables the useof two separate transmitters. In order to accommodate this, thefrequency range between the two transmitters needs to be large enough sothat the cutoff frequencies block the two transmitters from saturatingthe other's receivers. Because the two transmitters are perpendicular,the receivers from one transmitter are parallel to the other transmitterand only the frequency cutoff of the antennas will block the opposingtransmitter's signal.

FIG. 6 illustrates a phase shift between Rx antennas for a CW radarsystem according to one embodiment of the present invention. The CWradar system of the present invention looks for the blue channel (Rx₁)to lead to the red channel (Rx₂) in either an increase in signalstrength (constructive) or a decrease in signal strength (destructive)as the system gets closer to an object and/or target. However, it ispossible for some signals to simultaneously experience constructiveinterference on one Rx antenna and destructive interference on the otherRx antenna. When detecting multiple targets at various ranges, it ispossible for some signals to be constructive and others to bedestructive due to distance and orientation from the system. In order tocompare the blue channel (Rx₁) to the red channel (Rx₂), the CW radarsystem normalizes the signals using data recorded in the previous fewminutes and subtracts this signal data from the current signal. Theprevious few minutes of data serves as a baseline for the CW radarsystem. As more data is collected, the baseline is adjusted. Thisdynamic baseline adjustment accounts for all sources of signal noise andvariation and ensures that all signals from the CW radar system arenormalized, improving system accuracy and efficiency. If no targets werepresent, both channels would indicate signal readings of zero afternormalization. Due to fluctuations in electronics and other equipment,the CW radar system is operable to detect approximately −70 toapproximately −110 decibel watts (dBW) of signal from the combined noiseinputs. This equates to an overall detection sensitivity ofapproximately 1/1×10¹¹ Watt of signal. In one embodiment, the signalreceived by the CW radar system in the presence of an object and/ortarget is at least 45 dBW above the combined noise floor after postprocessing.

The phase (φ) difference between the multiple Rx antennas is a compositerelationship between the direct path signal, the condition of the oceansurface, the vibration in the system's structure, variations occurringat the tow line, and the object and/or target being detected. Themagnitude of the signal is proportional to the phase difference betweenthe two signals such that a larger phase difference results in astronger signal. Therefore, in effect the phase and magnitude of thetime difference signal are the same measurement, where one is easier toidentify at various times. In one embodiment, the system uses the changein phase signal to detect an object and/or target.

The wavelength in the Rx antenna(s) is equal to the wavelength in the Txantenna, only with a phase shift based on the distance from the Txantenna, the object/target, and the Rx antenna(s). In one embodiment ofthe present invention, when this distance is between approximately 59.7meters (m) and approximately 119.4 m, the signals create a destructiveinterference, decreasing the total signal strength below the directpath.

The wavelength (1/frequency) in the Rx antennas is equal to wavelengthin the Tx antenna(s), but the signals are phase-shifted based on thedistance from the Tx antenna(s) to the object and/or target and back tothe Rx antennas. Thus, the phase shift is associated with the differencein distance that the two Rx antennas are perceiving.

For example, if the CW radar system is transmitting at approximately 283Hz, the perceived wavelength is equivalent to approximately 59.7 massuming water salinity of approximately 4.95 Siemens, as opposed toapproximately 1,000,000 m if transmitted in open air. The path length isa measurement from Tx antenna-to-object/target-to-Rx antennas. In thisembodiment, the path length is equal to two-thirds of the wavelength, orapproximately 38.6 m, and produces constructive interference in anysignal returning from the object/target to the Rx antennas. The resultis a direct signal strength of approximately 3.5 dBW from the Tx antennato either Rx antenna, after amplification from the CW radar system ofthe present invention. The return signal from an object and/or targetthat is less than approximately 10 m away will cause the signal in theRx antennas to increase by more than approximately 1 dBW due toconstructive interference. Destructive interference will have theopposite effect and cause the signal to be lower in signal strength.

The CW radar system of the present invention detects a plurality ofphase shift samples from a plurality of samples. In one embodiment, theCW radar system is operable to detect between approximately 5-10 samplesof phase shift for every 256,000 samples recorded. Additionally,multiple effects are detected in the current system in addition to phaseshift between antennas. These include, but are not limited to,differences in signal strength between the Rx antennas and variations infrequency of the signals at each Rx antenna. Although the Tx antenna isproducing a constant tone/frequency, there are Doppler effects thatoccur due to vibrations in the physical structure of the system thatresult in signal differences between each Rx antenna.

FIG. 7A illustrates variances in signal strength between Rx₁ and Rx₂antennas for the Rx₁ antenna according to one embodiment of the presentinvention.

FIG. 7B illustrates variances in signal strength between Rx₁ and Rx₂antennas for the Rx₂ antenna according to one embodiment of the presentinvention.

FIG. 7C illustrates variances in frequency using a lower frequencyaccording to on embodiment of the present invention.

FIG. 7D illustrates variances in frequency using a Tx frequencyaccording to one embodiment of the present invention.

FIG. 7E illustrates variances in frequency when using a higher frequencyaccording to one embodiment of the present invention.

Location and Classification

In one embodiment, the CW radar system of the present invention isactive sensor-based using electrical conductivity. With an activesensor, signal strength, frequency, and direction can be increasedand/or controlled based on the Tx's inputs, polarization, and physicalcharacteristics. An active sensor system increases its operating rangeby controlling both Tx and Rx characteristics. Ferrous material,including, but not limited to, iron and steel, and non-ferrous material,including, but not limited to, gold, silver, copper, and/or aluminum,are actively excited by the Tx and the EM waves. This creates anelectrical current due to the material's conductivity. The physicalshape of an object and/or target will produce a return EM wave that isdetected by the CW radar system's Rx antennas. The characteristics ofthe return EM wave are a result of the relationship between the Txantennas and signals, the Rx antennas and signals, and all conductivematerial composing and surrounding the total system. Material, such assand, soil, and/or rock, has such low conductivity that they appeartransparent to the Rx antennas, while all conductive materials willproduce some level of detection in the Rx antennas.

TABLE 1 Conductivity of Non-Ferrous & Ferrous Metals MaterialConductivity (S/m) Sliver  6.3E+07 Copper (annealed) 5.80E+07 Gold4.11E+07 Aluminum 3.77E+07 Brass (66% Cu, 34% Zn) Copper (annealed)2.56E+07 Carbon Tungsten 1.79E+07 Zinc 1.67E+07 Cobalt 1.60E+07 Nickel1.43E+07 Iron 1.03E+07 Platinum 9.52E+06 Tin 9.17E+06 Lead 4.57E+06Titanium 2.38E+06 Stainless Steel 1.45E+06 Mercury (liquid) 1.04E+06Bismuth 8.70E+05 Carbon 2.00E+05 Distilled Water 1.00E−04 Dry sandy soil1.00E−03 Fresh water 1.00E−02 PET 1.00E−21

In one embodiment, the CW radar system transmits a signal in the Txantenna(s) by creating a specific frequency through the use of a signalgenerator. In one embodiment, the signal generator functionalityincludes, but is not limited to, dual channel output, a sampling rate ofapproximately 150 MegaSamples per second (MSa/s), generation oflower-jitter Pulse waveforms, support for analog and digital modulationtypes, sweep and burst functions, a harmonics generator function, a highprecision frequency counter, standard interface compatibility (e.g., USBHost, USB device, LAN, etc.), a display, channel duplicationfunctionality, and/or remote control operability. In one embodiment, theCW radar system uses a SIGLENT SDG-1025 signal generator. In oneembodiment, the CW radar system uses a RIGOL DG-1022 signal generator.In another embodiment, the CW radar system uses a SIGLENT SDG-1032Xsignal generator. In another embodiment, the CW radar system uses awaveform signal generator.

In one embodiment, the CW radar system transmits a signal in the Txantenna(s) by using a transmitter computer to create a digital,differential sinewave signal, which is operable to be sent to adigitizer board. A low voltage (+/−1V) sinewave is produced and is thenused as an input into a sound stereo amplifier. In one embodiment, thesound stereo amplifier is operable to amplify the low voltage signal,thereby producing an output signal with power between approximately 3500watts (W) and approximately 5000 W, and is further operable to producean output signal with amplitude between approximately +/−20 V andapproximately +/−600 V. The voltage (power output) limitations of the Txsignals is restricted by the properties of the wires within the Txantennas. In one embodiment, the Tx antenna uses larger gauge wires andis operable to produce voltages in excess of 600V. In anotherembodiment, the Tx antenna produces signals between approximately 5-20V.

The output from the transmitter computer is a differential output (i.e.,two signals) that are 180 degrees out of phase from one another.Together, these two signals make up a sinusoidal wave.

The returning signal from the Rx antenna(s) is also a differentialsignal. The return signal is sent from the CW radar system's sensor headup through a data cable to a dinghy. The dinghy contains a globalpositioning system (GPS) that sends a GPS position through the datacable, along with all the differential signals from each Rx antenna,back to a towing vessel. The incoming signals to the towing vessel arereceived by at least one impedance matching board that matches the Rxantenna impedance to that of the amplifier boards, which then pass thesignal to the receiving computer's digitizer board after amplification.In one embodiment, the impedance is fine-tuned for the CW radar systemsetup instead of having a set resistor value. In one embodiment, theimpedance matching does not drift and does not to be readjusted once itis matched. The incoming analog signal from the Rx antenna(s) isdigitized in order to be used by the CW radar system's source code. Inone embodiment, the GPS device used on the dinghy and the towing vesselare differential GPS devices.

FIG. 8 illustrates object detection ranges for a CW radar systemaccording to one embodiment of the present invention. The dot at thecenter represents the CW radar system. A combination of constructiveand/or destructive alternating bands indicate which zone theobject/target is located in based on the object/target's distance fromthe Tx/Rx antenna system. In one embodiment, the signal received by theouter channel (Rx₁ channel) is used to analyze the signal received bythe inner channel (Rx₂ channel) to determine an upward rise in signalstrength (constructive) and/or a downward drop in signal strength(destructive) as the CW radar system is towed/pulled over theobject/target. In order to compare the Rx₁ and Rx₂ channels, the signalsare normalized using a previously selected time interval of datacollected in the absence of an object/target, which is then subtractedfrom the current signal data. If no objects/targets were located orpresent, both channels would equate to zero.

In one embodiment, the CW radar system of the present invention usesthree principal time domain signals in order to locate objects/targets:signals in the forward Rx antenna, signals in the aft Rx antenna, andthe signal difference between the forward and aft Rx antennas. Thesethree signals are then analyzed with respect to energy, power, standarddeviation, and phase. All signals are coming from the variation ofsignals in the time domain.

By using multiple frequencies, the CW radar system of the presentinvention is able to not only detect and locate objects and/or targets,but classify them as well. This is performed using the relative signalstrength and phase between signals of different frequencies, enablingthe CW radar system to distinguish between materials including, but notlimited to, all ferrous and non-ferrous metals (i.e. gold and/or silverobjects). Signals of any frequency can be used to detect all metalobjects, but the spectral response or relationship between thefrequencies determines the type of metal the object is made of. If anobject(s) is made from multiple metal types, the return signal of the CWradar system is a pattern that indicates the individual metalsassociated with an object and/or target. Because different metals havedifferent conductivities, they will reflect each frequency differently.The signal response from an object and/or target also depends on if theobject and/or target is located in a constructive or destructiveinterference zone. The location and width of the constructive anddestructive zone is different for each frequency. Therefore, the CWradar system is operable to detect and classify objects and/or targetsusing the spectroscopy response of objects and/or targets using multiplefrequencies.

FIG. 9 illustrates a precision detector for a CW radar system accordingto one embodiment of the present invention. The CW radar system iscapable of using a single Tx antenna and a single Rx antenna toprecisely locate objects and/or targets. The single Tx antenna and thesingle Rx antenna are connected to one another via a non-conductingpipe/rigid structure. When the CW radar system is stationary, thisantenna setup is operable to locate and detect objects and/or targets.In a stationary state, power and frequency will vary across the CW radarsystem while data is being collected. Moreover, by using a single Txantenna and a single Rx antenna when the CW radar system is stationary,the CW radar system is operable to pinpoint an object and/or target anddetermine the object's and/or target's precise depth. In one embodiment,the single Tx antenna and single Rx antenna are the same antennasalready incorporated within the CW radar system. In another embodiment,the single Tx and single Rx antenna setup is a separate, detachableantenna setup from the main body of the CW radar system.

The constructive and destructive zones for the CW radar system of thepresent invention are determined using the distance from the CW radarsystem to an object/and or target and the return path of the Tx signalto the Rx antennas. This distance represents the total distanceassociated with a signal from its transmission from the Tx antenna, toits reception by the Rx antenna(s). This distance accounts forfrequencies in use by the CW radar system as well.

FIG. 10 illustrates a graph indicating constructive and destructivesignals associated with locating an object in a saltwater environmentaccording to one embodiment of the present invention. When an objectand/or target is detected by the CW radar system in a constructive zone,an increase in signal strength is detected as the CW radar systemapproaches the object and/or target, and a decrease in signal strengthis detected as the CW radar system moves away from the object and/ortarget. When an object and/or target is detected by the CW radar systemin a destructive zone, a decrease in signal strength is detected as theCW radar system approaches the object and/or target, and an increase insignal strength is detected as the CW radar system moves away from theobject and/or target. In one embodiment, this appears on a graph as adouble-hump shape, indicating that all Rx antennas detected the objectand/or target.

FIG. 11A illustrates a graph indicating constructive and destructivezones over time created by the signals collected using the sensor head,a tow vessel, and a dinghy associated with locating an object in asaltwater environment according to one embodiment of the presentinvention. The movement of the sensor head associated with a towing bythe vessel system determines when and where signals are transmitted andreceived by the corresponding Tx and Rx antennas. In addition, the CWradar system must monitor its output energy product.

FIG. 11B illustrates a graph indicating the energy product for a CWradar system according to one embodiment of the present invention.

FIG. 11C illustrates a graph indicating antenna signal strengthassociated with constructive and destructive zones of a CW radar systemaccording to one embodiment of the present invention.

FIG. 11D illustrates a graph indicating a fore and aft antenna energyproduct associated with constructive and destructive zones of a CW radarsystem according to one embodiment of the present invention.

In one embodiment, a towing vessel attaches a tow line and/or tow cableto a dinghy, wherein the dinghy is attached, via a second tow lineand/or tow cable, to the sensor head of the CW radar system of thepresent invention. In one embodiment, the CW radar system includes a towline and/or tow cable for connecting the towing vessel to the dinghy anda tow line and/or tow cable for connecting the dinghy to the CW radarsystem as well as a data tow line and/or data tow cable connecting thetowing vessel to the dinghy and a data tow line and/or data tow cableconnecting the dinghy to the CW radar system. In one embodiment, thedinghy includes a global positioning system (GPS) receiver. Because theCW radar system is located underwater, the GPS receiver must be placedon the attached dinghy and not the CW radar system. An initialcalibration of the CW radar system components is performed and abaseline for object and/or target geolocation data is established. Inone embodiment, the baseline signal for a constructive zone is louderand the signal is elevated. In one embodiment, the negative energy in adestructive zone is quieter. The towing vessel travels in a line over atarget survey area at an optimum speed. The CW radar system is operableat speeds between approximately 0 to >30 kts. In one embodiment, theoptimum speed of the towing vessel is between approximately 3 kts to 8kts to reduce vibrational noise interference. Once the towing vessel,the dinghy, and the CW radar system have traveled over the target surveyarea, the towing vessel turns approximately 90° and specifies a new lineof travel over the target survey area. In one embodiment, the towingvessel turns clockwise. In another embodiment, the towing vessel turnscounterclockwise. This new line is covered by the towing vessel, thedinghy, and the CW radar system. In one embodiment, the CW radar systemis operable to send and receive signals within a range of approximately30-100 m from each side of the CW radar system when traveling in a line,resulting in a total swath width of approximately 60-200 m in one pass.In another embodiment, the CW radar system is operable to send andreceive signals within a range of 200 m from either side of the CW radarsystem when traveling in a line, resulting in a total swath width of 400m per pass. In one embodiment, the lines of travel taken by the towingvessel, the dinghy, and the CW radar system over the target survey areaare approximately 100 m apart from each other.

In one embodiment, the towing vessel, the dinghy, and the CW radarsystem traverse the same part of the target survey area multiple timesin order to more accurately identify the size, structure, shape, andcomposition of the object and/or target. This process is repeated in aset pattern until the target survey area has been completely mapped bythe towing vessel, the dinghy, and/or the CW radar system. By travellingover the target survey area in a designated pattern using the towingvessel, the dinghy, and the CW radar system, the CW radar systemcollects data that can be associated with the geolocation of underwaterferrous and/or non-ferrous objects. This is because when the CW radarsystem travels over an object and/or target, a change in signal strengthis detected followed by a change in signal strength in the oppositedirection as the towing vessel, the dinghy, and the CW radar systemmoves away from a detected object and/or target. When the data has beenprocessed, the CW radar system returns Gaussian-like curves in the areawhere an object and/or target has been located, indicating detectionfrom the front and rear antennas of the CW radar system. In oneembodiment, the CW radar system returns lines and/or scatter trailsindicating an object and/or target. The CW radar system passes over anarea multiple times in order to generate tighter lines around the objectand/or target. In one embodiment, the CW radar system is connecteddirectly to the towing vessel via a single tow line, without the use ofa connecting dinghy.

In one embodiment, the CW radar system detects changes in signalstrength the first time it passes over an object and/or target. The CWradar system then passes over the same area again and varies the powerlevel of the signal in order to collect more data on the object and/ortarget. A lower power signal provides more detail and higher fidelityimages of the object and/or target. In one embodiment, the power levelof the signal depends on the pattern used to survey the area. In oneembodiment, the CW radar system makes tighter passes over the same partof the target survey area in order to detect more information about anobject and/or target in that part of the target survey area. In oneembodiment, the pattern that the CW radar system takes over the targetarea and the power variations in the signal are set before the CW radarsystem begins traversing the target area in order to capture full detailof the target area. In another embodiment, the pattern that the CW radarsystem takes over the target area and the power variations in the signalare dependent on the readings of the Rx antenna. When the CW radarsystem detects changes in signal strength the first time it passes overan object and/or target, it modifies the subsequent path and signaltransmission in order to obtain further information about the detectedobject and/or target. In one embodiment, the power level of the signalused to identify the object and/or target is controlled by the gain ofthe Rx amplifier board. In another embodiment, the power level of thesignal used to identify the object and/or target is controlled by the Txantennas. In yet another embodiment, the power level of the signal usedto identify the object and/or target is controlled by both the Tx andthe Rx antennas. In one embodiment, the CW radar system is operable toidentify the size, structure, and shape of an object and/or target withmultiple radar readings. For example, the CW radar system is operable toidentify ribs on a barge and brass shells in an underwater environment.

FIG. 12A illustrates a three-dimensional (3D) underwater depth mapindicating areas where no objects and/or targets were detected by a CWradar system according to one embodiment of the present invention. Ifthe CW radar system detects an object and/or target, a spike in signalstrength would have been detected as the bow and aft Rx antennasapproached and moved away from underwater objects and/or targets. Thelack of a significant increase/decrease in signal strength (blue)compared to background noise indicates that no objects and/or targetswere detected. The background noise level typically will vary slightlyas indicated in the small spikes in the blue peaks. An object and/ortarget that is closer to the CW radar system will result in a strongersignal reading by the Rx antennas.

FIG. 12B illustrates a 3D underwater depth map indicating multipledetected objects by a CW radar system according to one embodiment of thepresent invention. The multiple blue-green and yellow colored spikespresent on the 3D underwater depth map indicate that both the bow andaft Rx antennas detected an object and/or target (i.e., multipleincreases and decreases in signal strength). These spikes occur as thebow and aft Rx antennas approach and move away from underwater objectsand/or targets.

FIG. 13A illustrates a 3D underwater depth map indicating the locationof objects according to one embodiment of the present invention. Once asurvey for a target area is performed using the CW radar system of thepresent invention, the collected data is operable for display viamapping software. In one embodiment, the collected data indicatesinformation including, but not limited to, an object and/or targetdepth, a geolocation for an object and/or target, a north value, a westvalue, an east value, and/or a south value. In one embodiment, thegeolocation for an object and/or target is a set of coordinate points.

FIG. 13B lists all of the labels in FIG. 13A representing differentgeographic locations for detected objects according to one embodiment ofthe present invention.

FIG. 14A illustrates a two-dimensional (2D) underwater depth mapindicating location coordinates for a detected object according to oneembodiment of the present invention. This underwater depth map indicatesa sampling region for the CW radar system. The 2D underwater depth mapis shown from a South-to-North and West-to-East perspective.

FIG. 14B lists all of the labels in FIG. 14A representing differentgeographic locations for detected objects according to anotherembodiment of the present invention.

FIG. 15A illustrates a 2D underwater depth map indication locationcoordinates for detected objects according to another embodiment of thepresent invention.

FIG. 15B lists all the labels in FIG. 15A representing differentgeographic locations for detected objects according to one embodiment ofthe present invention.

FIG. 16A illustrates a surveying operation with a CW radar systemaccording to one embodiment of the present invention. The CW radarsystem is connected to a towing vessel. As the CW radar system travelsover ferrous and/or non-ferrous metal objects, the CW radar system isoperable to identify a plurality of buried test sites.

FIG. 16B illustrates a surveying operation with a CW radar systemconnected to a towing vessel according to one embodiment of the presentinvention. The CW radar system is connected to the towing vessel via atow cable and at least one data cable. The tow cable includes aplurality of tow cable floats, wherein the plurality of tow cable floatsare operable to prevent the tow cable and the at least one data cablefrom sinking below the surface of the water when the towing vessel isnot moving.

FIG. 17A illustrates a 2D underwater heatmap indicating the geolocationof detected objects according to one embodiment of the presentinvention. The 2D underwater heatmap further includes an indication ofdensity and/or intensity. In one embodiment, the 2D underwater heatmapis overlayed with magnetometer search tracks. When overlayed with themagnetometer, the CW radar system is able to locate all metal objectsand/or targets, while simultaneously eliminating the ferrous objectsand/or targets. In one embodiment, the return phase and amplitudedifferences in each heat map are used to distinguish between specificmetal types. In one embodiment, the identification of different metaltypes is done automatically and in near real-time.

FIG. 17B lists all of the labels in FIG. 17A representing differentpriority zones on a 2D underwater heatmap for a CW radar systemaccording to one embodiment of the present invention, where priorityzones represent areas where at least one or more object(s) and/ortarget(s) were detected by the CW radar system.

FIG. 18 illustrates a 2D underwater depth map indicating the geolocationof detected objects according to another embodiment of the presentinvention.

FIG. 19A illustrates a 2D underwater heatmap indicating the geolocationof detected objects according to another embodiment of the presentinvention. The 2D underwater heatmap includes a plurality of priorityzones, indicating analyzed areas with detected objects. In addition, the2D underwater heatmap further includes a density and/or an intensity foreach priority zone.

FIG. 19B lists all of the labels in FIG. 19A representing differentpriority zones on a 2D underwater heatmap for a CW radar systemaccording to one embodiment of the present invention.

FIG. 20A illustrates a 2D underwater heatmap indicating a CW radarsystem traveling path and the geolocation of detected objects accordingto another embodiment of the present invention. The 2D underwaterheatmap indicates priority zones detected by the CW radar systems. The2D underwater heatmap further includes an indication of intensity and/ordensity for each priority zone and/or detected object and/or target.

FIG. 20B lists all the labels in FIG. 20A representing differentgeographic locations for detected objects according to one embodiment ofthe present invention.

FIG. 21A illustrates a 2D graph indicating underwater reef and submergedsandbars (in dark brown) and a travel route for a CW radar systemaccording to one embodiment of the present invention. At the beginningof a surveying operation, a target region is established. With thetarget region established, a towing vessel begins towing the CW radarsystem in a line pattern (i.e., the travel route) over the targetregion. In one embodiment, the towing vessel is connected to the CWradar system via a dinghy. A towing cable and a data cable connect thetowing vessel to the dinghy, and the dinghy connects to the CW radarsystem via a towing cable and/or data cable. In one embodiment, thetowing vessel is connected to the CW radar system via a towing cableand/or data cable in addition to a dynamic winch system. The dynamicwinch system is operable to facilitate the sensor head depth duringtowing. In one embodiment, the towing vessel is connected to the CWradar system via a towing cable and/or data cable in addition to the useof a dynamic down plane system on or ahead of the sensor head. Thedynamic down plane system is operable to facilitate the sensor headdepth during towing.

FIG. 21B illustrates a 2D heatmap graph indicating a travel route for aCW radar system according to one embodiment of the present invention. Byrepeatedly crossing over a target region, the CW radar system isoperable to detect objects and/or targets with greater accuracy. This ispossible using the combination of the bow and aft Rx antennas of the CWradar system, providing multiple opportunities for object and/or targetdetection.

The CW radar system of the present invention includes at least oneamplifier board. Current commercially-available amplifier boards areunable to meet the amplification and dynamic range requirements of thepresent invention. Commercially available amplifier boards typicallyamplify at specific levels or ranges (e.g., 20-40 dB, 40-60 dB, 60-80dB, etc.). More specifically, these commercial amplifier boards onlyenable a user to step through each decibel range at limited levels(i.e., by one-half or full decibels at each one of the availablelevels). Thus, these commercial amplifier boards are not sensitiveenough and/or do not offer enough dynamic and detailed control for theCW radar system of the present invention. While the amplifier board(s)of the CW radar system are digital-to-analog (D-A) and analog-to-digital(A-D) amplifier boards, the CW radar system requires a step size ofapproximately 1/1,000 decibels (dB), which is not typically availablewith commercial amplifiers and amplifier boards.

Moreover, commercial amplifier boards experience difficulties whenbalancing two antennas within close proximity to one another, including,but not limited to, issues balancing the signal-to-noise ratio and/orissues relating to overall power output for a radar system. Traditionalamplifier boards cannot reach the decibel ranges required of the CWradar system of the present invention. The CW radar system requires theamplifier board to be able to operate between approximately 60 dB toapproximately 150 dB. The CW radar system also requires the amplifierboard to compensate for the DC biasing offset voltage without losingsystem gain. These functions are accomplished through hardware circuitrydesign and software control logic.

Due to the extremely low frequency (ELF) signals involved, an amplifierboard built to handle the specific search frequencies is required,incorporating a direct current (DC) voltage to less than 10 Volts (V).There are no commercially available amplifier boards with both dynamicrange and amplification operable to achieve the necessary precision ofthe CW radar system of the present invention.

FIG. 22A illustrates an amplifier board for a CW radar system accordingto one embodiment of the present invention. The amplifier boardincludes, but is not limited to, an output stage and/or an input stage.The amplifier board is operable to handle output voltages betweenapproximately 10 V to more than approximately 600 V through the Txantenna(s). In one embodiment, the amplifier board of the presentinvention is a three-stage circuit. The first stage is an n-amp(instrumentation amplifier), that amplifies the differential voltagebetween input wires. A differential voltage is used to create the signalbecause the input to the amplifier board comes from a dipole antennathat is not grounded to the amplification board. The first stage isoperable to provide up to approximately 80 decibels (dBs) of gain. Inone embodiment, the first stage n-amp is operable to provide more thanapproximately 80 dBs of gain. The second stage is an operationalamplifier (op-amp), operable to provide up to approximately 40 dBs ofgain. In one embodiment, the second stage op-amp is operable to providemore than approximately 40 dBs of gain. The third stage is a band-passfilter, operable to provide approximately 2 dB of gain. In oneembodiment, the third stage band-pass filter is operable to provide morethan approximately 2 dB of gain.

FIG. 22B illustrates a pin configuration diagram for an amplifier boardfor a CW radar system according to one embodiment of the presentinvention. In one embodiment, the amplifier is an AD622 amplifier board.AD622 amplifiers require only one external resistor to set any gainbetween approximately 2 dBs and approximately 100 dBs. For a gain of 1dB, no external resistor is required.

FIG. 22C illustrates a pin connection diagram for an amplifier board fora CW radar system according to one embodiment of the present invention.In one embodiment, the amplifier board is an AD8421 amplifier board.AD8421 amplifier boards operate at a low cost, low power, extremely lownoise, ultralow bias current, and include high speed instrumentationsuited for signal conditioning and data acquisition applications.

FIG. 22D illustrates a pin configuration and function diagram for anamplifier board for a CW radar system according to another embodiment ofthe present invention.

FIG. 22E illustrates a pin configuration and function diagram for anamplifier board for a CW radar system according to another embodiment ofthe present invention.

FIG. 22F illustrates a chart depicting the flow of signal through anamplifier board for a CW radar system according to one embodiment of thepresent invention. The chart depicts four stages of signal flowthroughout the amplifier board. While stage one is always required, thesignal flow is operable to flow through any combination of the remainingstages. By eliminating a stage from the signal flow, the overall noiseadded to the CW radar system is reduced. In one embodiment, the flow ofsignal through the amplifier board is multi-stage and the amplificationvalues and stages used are all computer controlled. The amplifier boardfurther includes a wiring harness operable to read all amplifier boardinputs and settings, and then send the proper setting signals in orderto calibrate each board in the system. Each wiring harness includes aplurality of output control cables to Rx antennas and at least onecomputer input side. In one embodiment, the flow of the signal throughthe amplifier board depends on the location of the boat and the presenceof radiofrequency interference and noise from external sources. When theboat is closer to a land mass, there is increased interference frompower grids and other signal sources. In one embodiment, the power gridinterference includes a 60 Hz signal. In another embodiment, additionalharmonics cause further interference in the system. In one embodiment,the four-stage amplifier board is operable to eliminate the interferencevia a series of filters. In another embodiment, the signal does not flowthrough all four stages of the amplifier board. In one embodiment, thestages of amplification are chosen to reduce the amount of overall noiseadded to the CW radar system.

FIG. 23 lists a table for a primary gain stage of an amplifier board fora CW radar system according to one embodiment of the present invention.The primary gain stage includes resistor combinations and settings foran Rx antenna gain controller.

FIG. 24 lists a table for a secondary gain stage of an amplifier boardfor a CW radar system according to one embodiment of the presentinvention. The secondary gain stage includes resistor settings for an Rxantenna gain controller. The various stage settings are measured inunits of ohms (Ω). In addition, the stage settings include resistorsettings for an Rx antenna gain controller.

FIG. 25 lists a table for Stage One and Stage Two gain settings for anamplifier board for a CW radar system according to one embodiment of thepresent invention. The various stage settings are measured in units ofkiloohms (kΩ). In addition, the stage settings include resistor settingsfor an Rx antenna gain controller.

The amount of gain provided by the three-stage circuit setup isindividually determined for each Rx antenna. While the antennas used,both Tx and Rx, are interchangeable, they each have their owncapacitance and performance curves. In addition, correspondinglogic-controlled circuitry enables capacitance matching between thetransmitter, amplifier, and antenna(s). This requires that each antennahave its own amplification settings, or gain, when used as a Rx antenna.In addition to this gain, the system of the present invention usesoversampling to provide another gain due to processing gain. In oneembodiment, the oversampling is operable to provide approximately 24 dBsof gain. In one embodiment, the CW radar system is operable to sample atapproximately 256,000 times a second. In addition, the amplifier boardincludes both low and high frequency pass filters, with gain controlsfrom less than approximately 2 dB to more than approximately 130 dB.

FIG. 26 lists a table for gain calculations for an amplifier board for aCW radar system according to one embodiment of the present invention.The stage settings are measured in units of ohms (Ω). In addition, thestage settings include resistor settings for an Rx antenna gaincontroller.

FIG. 27 lists a table for Stage One and Stage Two gain settings for anamplifier board for a CW radar system according to another embodiment ofthe present invention.

FIG. 28A lists a table for resistance values for an amplifier board fora CW radar system according to one embodiment of the present invention.

FIG. 28B lists a table for additional resistance values for an amplifierboard for a CW radar system according to one embodiment of the presentinvention.

FIG. 28C lists a table for additional resistance values for an amplifierboard for a CW radar system according to one embodiment of the presentinvention.

In one embodiment, the amplifier board(s) of the CW radar system of thepresent invention operate in four stages. The first stage requires theCW radar system to turn multiple signals into a single signal, used forobject and/or target geolocation. Next, a low-pass anti-aliasing filteris applied to the single signal. This low-pass filter removesunnecessary frequencies from the system. The third and fourth stages areidentical, and involve the removal of noise associated with any directcurrent (DC) offset in order to isolate the signal. Each stageintroduces between approximately 1.5 dBs to approximately 271 dBs gainper stage. Once the signal is isolated, the various Tx and Rx antennasare balanced, resulting in an output indicating the geolocation of anobject and/or target. In one embodiment, the amplifier board isdigitally controlled. In one embodiment, the amplifier board isautomatically controlled. In another embodiment, the amplifier enables auser to select the cutoff frequency from a range of approximately 106 Hzto approximately 3,000 Hz. For low-band frequencies, the cutofffrequency is between approximately 106 Hz and approximately 280 Hz. Formid-band frequencies, the cutoff frequency is between approximately 220Hz and approximately 650 Hz. For high-band frequencies, the cutofffrequency is between approximately 500 Hz and approximately 3,000 Hz.

FIG. 29 illustrates an amplifier board for a CW radar system accordingto another embodiment of the present invention.

FIG. 30 illustrates an amplifier board for a CW radar system accordingto another embodiment of the present invention.

The raw signals received by the Rx antennas are on the order of apico-volt or less. These ultra-faint signals are amplified by betweenapproximately 70 dB and approximately 120 dB of gain, with a maximumboard gain capability of more than approximately 155 dB. In oneembodiment, the typical gain of the system is between approximately100-110 dB in order to avoid saturation. In one embodiment, theamplification of the at least one amplifier board optimizes thesignal-to-noise ratio (SNR) to minimize noise from vibrations and othersources. In one embodiment, the at least one amplifier board iscontained in a two-step noise reduction system. First, impedancematching and receiver amplifier boards are housed inside shielded andgrounded metal boxes functioning as a Faraday cage, preventingelectromagnetic interference (EMI). Second, each box is housed inside athermo-electric cooler and/or heater in order to maintain a nearconstant operating temperature. This prevents thermal noise fromentering the amplifier boards in any environmental condition.

All connectors entering the EMI boxes are shielded and grounded. Inaddition, any openings present on the EMI boxes are covered with analuminum mesh, wherein the mesh is also grounded to the EMI box. Inanother embodiment, the mesh is a copper mesh. At the frequencies usedby the CW radar system, the aluminum mesh visually appears “open,” butin reality, is an electrical barrier to all frequencies belowapproximately 10,000 Hz. Without EMI shielding, the amplificationprocess is reduced by approximately 30-60 dB which is insufficient forthe signals coming from the Rx antennas. In one embodiment, each Rxantenna in the CW radar system has its own EMI box. Each EMI box is thenplaced inside a refrigerated container for climate control. In oneembodiment, the frequencies used by the CW radar system areapproximately 3,000 Hz or less.

Amplification occurs in two stages. The first stage involves directcurrent (DC) removal and isolation. The DC removal and isolationtechniques are described in Kresimir Odorcic (2008). “Zero DC offsetactive RC filter designs,” ThinkIR: The University of Louisville'sInstitutional Repository, which is incorporated herein by reference inits entirety. Stage two represents the digitally-controlledamplification stage. By using digital relays in conjunction with fixedresistors in series-parallel networks, the CW radar system is able todigitally change amplification values. These stages includeapproximately 1,000,000 linear gain steps that are capable ofamplification from approximately 35 dBs to approximately 156 dBs.

The amplifier boards used in the present invention account for allamplification processes, DC offset issues, and/or low-pass filteringrequirements.

The CW radar system requires the use of a digitizer, a hardware devicethat receives analog information, including light and/or sound, andrecords it digitally. This process is known as digitization. Thedigitizer board includes a connector box, an input device for receivinginput from a transmitter computing device, and/or an output device forsending output to a receiver computer device.

Digitizer boards used in the present invention are operable to takebetween approximately +10 volts (V) and approximately −10V. Duringoperation of the CW radar system, power levels fluctuate due to clutterand noise issues. By operating between approximately +10V andapproximately −10V, the CW radar system is able to avoid saturation thatoccurs at voltages greater than approximately +10V and less thanapproximately −10V. In addition, operating between the range ofapproximately +10V and approximately −10V requires approximately 3.5decibel watt (dBW) in power. When a detection and/or collectionoperation begins, the Rx antenna(s) start with a signal measuringapproximately 50 nanovolts (nV) with no object and/or target detected.

All of the hardware components of the CW radar system of the presentinvention are subject to constant temperature regulation as well. Whileno specific temperature is required, the system must operate at asingle, constant and/or near-constant temperature. In one embodiment,the temperature of the CW radar system is maintained using athermally-controlled refrigerator, containing the EMI-shielded amplifierboxes. The CW radar system temperature is maintained using coolingand/or heating. The refrigerator(s) holding the EMI-shielded amplifierboxes are operable to cool and/or heat the air around the amplifierboxes in order to reduce the amount of thermal drift in the impedancematching and amplifier electronics. By maintaining the temperature ofthe CW radar system at a constant and/or near-constant temperature, thesystem avoids experiencing large temperature swings which are operableto decrease system accuracy, efficiency, and/or operability.

In addition to temperature issues, the CW radar system of the presentinvention also accounts for alternating current (AC) power issues.Because the CW radar system is towed, in a saltwater environment, from avessel, the vessel presents a grounding problem to the system. On land,grounding issues are simple: AC wiring systems including a greengrounding wire, preventing shocks and electrocution. The groundconnection is completed by clamping the AC wiring system to a metalwater pipe or by driving a long copper stake into the ground. However,water-based vessels are not grounded the same. Many water-based vesselsmake use of a plate enabling the vessel to ground itself to the ocean.Grounding for water-based vessels represents an additional source ofnoise that the CW radar system of the present invention must accountfor.

Post Processing

Post processing software is used in conjunction with the CW radar systemof the present invention. Post processing software functionalityincludes, but is not limited to, eliminating variances in boat speed,eliminating GPS timing differences across all GPS receivers used duringcollection, eliminating variances in computer timing across allcomputers used during collection, eliminating variances associated withthe depth of the CW radar system, real-time or near real-time objectand/or target detection, survey automation, adjusting controls relatedto a towing vehicle's navigational capabilities, object and/or targetclassification, and/or automated object and/or target identification.Object and/or target classification includes, but is not limited to,size, location, and a potential material type. In one embodiment, thepost processing software used is MATLAB (available from MATHWORKS). Inone embodiment, the post processing software used is Python. In oneembodiment, the post processing software used is C/C++. In oneembodiment, the post processing software used is Java. In oneembodiment, the post processing software is operable to detect objectsand/or targets and their compositions in real time. In anotherembodiment, the post processing software is operable to detect objectsand/or targets and their compositions in near real time.

Post processing must also account for a direct current (DC) offset. DCoffset occurs when hardware components add DC current to audio signals.For example, an amplifier board of the present invention emits anadditional DC microvolt into the signals received by the Rx antenna(s).Due to the sensitivity of the system, this additional microvoltrepresents a major positive or negative shift in signal reception. Thisshift leads to a saturation in signal reception.

In addition, the CW radar system makes use of a multi-step process forspecifically identifying objects and/or targets of interest, as well asthe material each object and/or target is made of. In one embodiment,the multi-step process includes, but is not limited to, raw datacollection, frequency offset, frame stitching, narrow band filtering,and/or elimination of discontinuities.

Raw data collection refers to the continuous stream of data coming fromthe Rx antenna amplifier boards, as well as corresponding GPS locationdata using a towing vessel and a dinghy. In one embodiment, every ⅕^(th)second of data from the Rx antenna amplifier boards and thecorresponding GPS location data are recorded. This raw data collectionis performed using the above-mentioned digitizer boards. In oneembodiment, the digitizer boards are operable to digitize the raw dataat a rate of approximately one million bits per second. The CW radarsystem further oversamples the raw data in order to increase the overallsignal-to-noise ratio. In one embodiment, oversampling at a rate ofapproximately 250,000 samples per channel yields an increase in gain forthe system between approximately 18 dB and approximately 26 dB.

As the CW radar system of the present invention detects both amplitudesand phase returns from objects and/or targets on or under the oceanfloor, the frequency offset must be constantly monitored and correctedfor. Any transmit frequency will vary slightly with time andenvironmental changes due to the electronic equipment used. Therefore,the frequency offsets in the return signal in the Rx antennas must becontinually adjusted. A constant frequency offset function is applied tothe raw data as it is collected by the CW radar system in order tobalance out the transmit frequency variations.

The frame stitching process involves stitching the individual data filescollected by the CW radar system into an array, covering hours of datacollection. This frame stitching process additionally solves for GPS andtiming discontinuities. If a single micro-second of data is lost, thisresults in a discontinuity in the phase shifting, causing false signalsto be inserted into the collected data. In order to solve this problem,in one embodiment the CW radar system uses at least one GPS receiver inorder to reduce the loss of GPS data when closing one second of arraydata and starting a new second of array data.

Once the raw data has been stitched together, a narrow band tap filteris applied to the continuous signal in order to eliminate the vibrationand motion of the sensor head through the water. The narrow band tapfilter is adjustable depending upon the environmental conditionsincluding, but not limited to, sea-state, towing speed, depth, and/or atow distance of the CW radar system behind a towing vessel and/ordinghy.

The last post-processing step eliminates any discontinuity associatedwith last data in the large, multi-hour array of signal data. Oncediscontinuities are eliminated, the CW radar system creates a filtereddata set. Using this filtered data set, any aliasing effects areeliminated by taking a moving sixty-second window of data and furtherprocessing the center thirty seconds of data in the sixty-second window.The edges of the sixty-second data file are where the aliasing effectsmanifest, meaning the center thirty-seconds of data are free of theseeffects. In addition, the filtered data set is used to correct the phaseoffset between the bow Rx antenna(s) of a specific band when comparedagainst the aft Rx antenna(s) of the same specific band.

Once the filtered data set has been phase offset corrected, the compileddata array is used to analyze the surveyed area. Any statistical data isalso stored along with the compiled array, which are both then used inconjunction with the sensor head's GPS position with respect to thesurveyed area. In order to simplify the post-processing functions, areasbefore, during, and after a turn in a surveyed area are marked and setaside. This is because during a turn, the path of the CW radar systemthrough the water varies not only in direction, but also in speed,depth, and physical orientation relative to the surface of the water.This variance in shallow depth surveys (i.e., surveys in a body of waterwith a depth less than 100 ft.) causes a rotation of the CW radar systemwhen being towed from a towing vessel, such that the surface reflectionsfrom the ocean and any wave action cause excessive noise and/or falsetargeting within the collected data.

In one embodiment, the software of the CW radar system includes at leastone graphical user interface (GUI). The GUI is operable to displayinformation including, but not limited to, Tx antenna health, Rx antennahealth, object and/or target geolocation, a geolocation for the CW radarsystem, a geolocation for a dinghy, a system temperature indicator, avessel status indicator, a speed indicator, an environmental temperatureindicator, an object/and or target depth indicator, an object and/ortarget material, an object and/or target size, a Tx antenna signalstatus, and/or a Rx antenna signal status.

This functionality is achieved using a combination of the CW radarsystem's amplifier board and impedance matching boards. Impedancematching refers to designing input impedance of an electrical loadand/or the output impedance of its corresponding signal source in orderto maximize the power transfer and/or minimize signal reflection fromthe electrical load. The electrical and antenna components of thepresent invention have a corresponding impedance (i.e., impedance goingout from the amplifier output signal). When transmitting a specificsignal, the CW radar system of the present invention verifies that theimpedance associated with the electrical equipment sending the specificsignal matches the impedance of the Tx antenna sending out the signal.In addition, the return signal from the Rx antenna(s) must also matchits impedance.

FIG. 31A illustrates the top of an impedance matching board for a CWradar system according to one embodiment of the present invention.

FIG. 31B illustrates the bottom of an impedance matching board for a CWradar system according to one embodiment of the present invention.

The Tx antennas require their own specialized impedance matching board.The input to this impedance matching board comes from a sound systemamplifier and the output goes directly to the Tx antennas via a datacable.

In one embodiment, the amplifier and impedance matching boards are allcomputer controlled. This enables the system to automatically and/orautonomously balance all of the values present in order to maximize thesignal going out to the Tx antennas and the signal coming back from theRx antennas.

As previously mentioned, the CW radar system of the present inventionincludes a multiplicity of graphical user interfaces (GUIs), with GUIsincluding, but not limited to, three-dimensional (3D) maps for anunderwater environment, sonar transmission and receiving, object and/ortarget detection mapping, receiver controls, transmission controls,and/or two-dimensional (2D) maps for an underwater environment.

FIG. 32 illustrates a graphical user interface (GUI) for displayingobjects detected by a CW radar system according to one embodiment of thepresent invention. The GUI is operable to provide a three-dimensional(3D) map of a saltwater environment, indicating the presence of anydetected objects and/or targets. The 3D map of the saltwater environmentis able to be viewed from a West-to-East and South-to-North perspective.When objects are detected, the GUI displays a double-hump-like 3D image.This occurs because an object is first detected by the bow Rx antennasof the CW radar system, creating a rise in signal strength. Thisdetected signal strength drops as the bow of the CW radar system passesover the detected object. Then, as the aft Rx antennas of the CW radarsystem detect the object, a second rise in signal strength is detected.As the aft of the CW radar system moves away from the detected object, adrop in signal strength occurs. The combination of the bow and aft Rxantenna detections results in a double-hump-shape on the GUI, indicatingthat an object has been detected. In one embodiment, the CW radar systemis operable to detect and identify objects and/or targets in real timeor near-real time. The movement of the CW radar system generates 2D and3D images of the target survey area with a multiplicity of lines.

FIG. 33 illustrates a GUI for displaying objects detected by a CW radarsystem according to another embodiment of the present invention. The GUIdisplaying the 3D map of the saltwater environment is able to be viewedfrom a South-to-North and West-to-East perspective.

FIG. 34 illustrates a sonar GUI for a CW radar system according to oneembodiment of the present invention. The sonar GUI is operable todisplay elements including, but not limited to, a start recording time,an end recording time, a heading, a range, a distance, a measurement ofthe distance divided by a sonar ping, an altitude, a travel route, aninline stretch value, a range limit, a view selection drop-down box, achannel selection, a color scheme selection, an auto refresh option, acompass, a list of detected objects and/or targets, and/or a tileidentification (ID) number.

FIG. 35 illustrates a travel route GUI for a CW radar system accordingto one embodiment of the present invention. The travel route GUI isoperable to display information including, but not limited to, a travelroute for the CW radar system, an object and/or target detectionindication, and/or a depth value. The travel route for the CW radarsystem is displayed as a green line, indicating the positions the CWradar system has traveled over. As the CW radar system continuouslytravels over a target region, objects and/or targets are detected by theRx antennas at the bow and aft of the CW radar system. The stronger thereceived signal by the Rx antennas, the darker the indication on the map(i.e., the red dots on the map). A cluster of red dots is also anindication of a detected object and/or target, as this indicates astrong signal detected by the bow and aft Rx antennas. In oneembodiment, the travel route GUI is displayed using color images. In oneembodiment, the travel route GUI is displayed in black and white images.

FIG. 36A illustrates a two-dimensional (2D) map indicating a log scaleof a normalized energy product for a CW radar system with no detectedtargets according to one embodiment of the present invention. The lackof detected objects is indicated by the absence of connecting linesbetween target points. As the CW radar system travels over a region,objects are first detected by the bow Rx antennas and then detected asecond time by the aft Rx antennas. This detection pattern is visualizedby solid lines, indicating that an object and/or target was detected byboth sets of Rx antennas as the CW radar system passed over the objectand/or target.

FIG. 36B illustrates a 2D map indicating a log scale of a normalizedenergy product for a CW radar system with detected targets according toanother embodiment of the present invention. Detected objects areindicated by the presence of connecting red lines between target zones.These red lines indicate that both the bow and aft Rx antennas receiveda corresponding return signal from an object and/or target. This occursas the bow Rx antennas cross over a detected object and/or target andthen move away from the detected object and/or target, with the aft Rxantennas then detecting the object and/or target followed by an increasein distance from the object and/or target. Thus, an object is detectedby the CW radar system twice, once as the bow Rx antennas are towed overthe object and a second time as the aft Rx antennas are towed over theobject. This results in increased accuracy relating to object and/ortarget detection of both ferrous and non-ferrous metals in saltwaterenvironments.

FIG. 37A illustrates a 2D density and intensity map for a CW radarsystem according to one embodiment of the present invention.

FIG. 37B illustrates a 2D density map for a CW radar system according toone embodiment of the present invention.

FIG. 38 illustrates a GUI for displaying energy and frequency dataassociated with a CW radar system according to one embodiment of thepresent invention. The GUI is operable to display information including,but not limited to, a graph indicating an energy of difference of timedomain signals, a graph indicating a product of energy, a graphindicating a standard deviation from antennas and power density, a graphindicating a difference in power history, a survey track map, a boatspeed and/or direction, a time, a channel 1 frequency, a channel 1 powervalue, a channel 2 frequency, a channel 2 power value, a mean, astandard deviation, a frequency offset value, a set of average phasevalues, a peak frequency distance, and/or a normalized energy productvalue. The red and blue lines correspond to the signal return from twoRx antennas. The green line is the power density spectrum calculation,which is derived from the signal return of the Rx antennas. The GUI isfurther operable to display a survey track in the lower right corner ofthe GUI. In another embodiment, the GUI has a set(s) of user-definedwindows to monitor, track, and display various component(s), system(s),and external values.

FIG. 39 illustrates a GUI for displaying phase detail and power historydata associated with a CW radar system according to one embodiment ofthe present invention. The GUI is operable to display informationincluding, but not limited to, a graph indicating subsecond phasedetail, a graph indicating subsecond power history for both a bow andaft normalized energy product, and/or a graph indicating a subseconddifference power history using a mean and standard deviation. The blueand red lines correspond to a signal return from two Rx antennas. Thegreen line is a power density spectrum calculation derived from thesignal return from the two Rx antennas.

FIG. 40 is a schematic diagram of an embodiment of the inventionillustrating a computer system, generally described as 800, having anetwork 810, a plurality of computing devices 820, 830, 840, a server850, and a database 870.

The server 850 is constructed, configured, and coupled to enablecommunication over a network 810 with a plurality of computing devices820, 830, 840. The server 850 includes a processing unit 851 with anoperating system 852. The operating system 852 enables the server 850 tocommunicate through network 810 with the remote, distributed userdevices. Database 870 is operable to house an operating system 872,memory 874, and programs 876.

In one embodiment of the invention, the system 800 includes a network810 for distributed communication via a wireless communication antenna812 and processing by at least one mobile communication computing device830. Alternatively, wireless and wired communication and connectivitybetween devices and components described herein include wireless networkcommunication such as WI-FI, WORLDWIDE INTEROPERABILITY FOR MICROWAVEACCESS (WIMAX), Radio Frequency (RF) communication including RFidentification (RFID), NEAR FIELD COMMUNICATION (NFC), BLUETOOTHincluding BLUETOOTH LOW ENERGY (BLE), ZIGBEE, Infrared (IR)communication, cellular communication, satellite communication,Universal Serial Bus (USB), Ethernet communications, communication viafiber-optic cables, coaxial cables, twisted pair cables, and/or anyother type of wireless or wired communication. In another embodiment ofthe invention, the system 800 is a virtualized computing system capableof executing any or all aspects of software and/or applicationcomponents presented herein on the computing devices 820, 830, 840. Incertain aspects, the computer system 800 is operable to be implementedusing hardware or a combination of software and hardware, either in adedicated computing device, or integrated into another entity, ordistributed across multiple entities or computing devices.

By way of example, and not limitation, the computing devices 820, 830,840 are intended to represent various forms of electronic devicesincluding at least a processor and a memory, such as a server, bladeserver, mainframe, mobile phone, personal digital assistant (PDA),smartphone, desktop computer, netbook computer, tablet computer,workstation, laptop, and other similar computing devices. The componentsshown here, their connections and relationships, and their functions,are meant to be exemplary only, and are not meant to limitimplementations of the invention described and/or claimed in the presentapplication.

In one embodiment, the computing device 820 includes components such asa processor 860, a system memory 862 having a random access memory (RAM)864 and a read-only memory (ROM) 866, and a system bus 868 that couplesthe memory 862 to the processor 860. In another embodiment, thecomputing device 830 is operable to additionally include components suchas a storage device 890 for storing the operating system 892 and one ormore application programs 894, a network interface unit 896, and/or aninput/output controller 898. Each of the components is operable to becoupled to each other through at least one bus 868. The input/outputcontroller 898 is operable to receive and process input from, or provideoutput to, a number of other devices 899, including, but not limited to,alphanumeric input devices, mice, electronic styluses, display units,touch screens, signal generation devices (e.g., speakers), or printers.

By way of example, and not limitation, the processor 860 is operable tobe a general-purpose microprocessor (e.g., a central processing unit(CPU)), a graphics processing unit (GPU), a microcontroller, a DigitalSignal Processor (DSP), an Application Specific Integrated Circuit(ASIC), a Field Programmable Gate Array (FPGA), a Programmable LogicDevice (PLD), a controller, a state machine, gated or transistor logic,discrete hardware components, or any other suitable entity orcombinations thereof that can perform calculations, process instructionsfor execution, and/or other manipulations of information.

In another implementation, shown as 840 in FIG. 40, multiple processors860 and/or multiple buses 868 are operable to be used, as appropriate,along with multiple memories 862 of multiple types (e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core).

Also, multiple computing devices are operable to be connected, with eachdevice providing portions of the necessary operations (e.g., a serverbank, a group of blade servers, or a multi-processor system).Alternatively, some steps or methods are operable to be performed bycircuitry that is specific to a given function.

According to various embodiments, the computer system 800 is operable tooperate in a networked environment using logical connections to localand/or remote computing devices 820, 830, 840 through a network 810. Acomputing device 830 is operable to connect to a network 810 through anetwork interface unit 896 connected to a bus 868. Computing devices areoperable to communicate communication media through wired networks,direct-wired connections or wirelessly, such as acoustic, RF, orinfrared, through an antenna 897 in communication with the networkantenna 812 and the network interface unit 896, which are operable toinclude digital signal processing circuitry when necessary. The networkinterface unit 896 is operable to provide for communications undervarious modes or protocols.

In one or more exemplary aspects, the instructions are operable to beimplemented in hardware, software, firmware, or any combinationsthereof. A computer readable medium is operable to provide volatile ornon-volatile storage for one or more sets of instructions, such asoperating systems, data structures, program modules, applications, orother data embodying any one or more of the methodologies or functionsdescribed herein. The computer readable medium is operable to includethe memory 862, the processor 860, and/or the storage media 890 and isoperable be a single medium or multiple media (e.g., a centralized ordistributed computer system) that store the one or more sets ofinstructions 900. Non-transitory computer readable media includes allcomputer readable media, with the sole exception being a transitory,propagating signal per se. The instructions 900 are further operable tobe transmitted or received over the network 810 via the networkinterface unit 896 as communication media, which is

operable to include a modulated data signal such as a carrier wave orother transport mechanism and includes any delivery media. The term“modulated data signal” means a signal that has one or more of itscharacteristics changed or set in a manner as to encode information inthe signal.

Storage devices 890 and memory 862 include, but are not limited to,volatile and non-volatile media such as cache, RAM, ROM, EPROM, EEPROM,FLASH memory, or other solid state memory technology; discs (e.g.,digital versatile discs (DVD), HD-DVD, BLU-RAY, compact disc (CD), orCD-ROM) or other optical storage; magnetic cassettes, magnetic tape,magnetic disk storage, floppy disks, or other magnetic storage devices;or any other medium that can be used to store the computer readableinstructions and which can be accessed by the computer system 800.

In one embodiment, the computer system 800 is within a cloud-basednetwork. In one embodiment, the server 850 is a designated physicalserver for distributed computing devices 820, 830, and 840. In oneembodiment, the server 850 is a cloud-based server platform. In oneembodiment, the cloud-based server platform hosts serverless functionsfor distributed computing devices 820, 830, and 840.

In another embodiment, the computer system 800 is within an edgecomputing network. The server 850 is an edge server, and the database870 is an edge database. The edge server 850 and the edge database 870are part of an edge computing platform. In one embodiment, the edgeserver 850 and the edge database 870 are designated to distributedcomputing devices 820, 830, and 840. In one embodiment, the edge server850 and the edge database 870 are not designated for distributedcomputing devices 820, 830, and 840. The distributed computing devices820, 830, and 840 connect to an edge server in the edge computingnetwork based on proximity, availability, latency, bandwidth, and/orother factors.

It is also contemplated that the computer system 800 is operable to notinclude all of the components shown in FIG. 40, is operable to includeother components that are not explicitly shown in FIG. 40, or isoperable to utilize an architecture completely different than that shownin FIG. 40. The various illustrative logical blocks, modules, elements,circuits, and algorithms described in connection with the embodimentsdisclosed herein are operable to be implemented as electronic hardware,computer software, or combinations of both. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application (e.g., arranged in adifferent order or partitioned in a different way), but suchimplementation decisions should not be interpreted as causing adeparture from the scope of the present invention.

FIG. 41 illustrates an amplifier board for a CW radar system accordingto one embodiment of the present invention.

FIG. 42 illustrates an amplifier board for a CW radar system accordingto another embodiment of the present invention.

FIG. 43 illustrates an amplifier board for a CW radar system accordingto yet another embodiment of the present invention.

FIG. 44 illustrates an amplifier board for a CW radar system accordingto yet another embodiment of the present invention.

FIG. 45 illustrates an amplifier board for a CW radar system accordingto yet another embodiment of the present invention.

FIG. 46 illustrates an amplifier board for a CW radar system accordingto yet another embodiment of the present invention.

The above-mentioned examples are provided to serve the purpose ofclarifying the aspects of the invention, and it will be apparent to oneskilled in the art that they do not serve to limit the scope of theinvention. By nature, this invention is highly adjustable, customizableand adaptable. The above-mentioned examples are just some of the manyconfigurations that the mentioned components can take on. Allmodifications and improvements have been deleted herein for the sake ofconciseness and readability but are properly within the scope of thepresent invention.

The invention claimed is:
 1. A radar system for detecting ferrous andnon-ferrous metals in underwater environments, comprising: at least onetowing vessel configured to traverse a target area; an antenna systemincluding at least one signal generator, at least one transmitter (Tx)antenna, at least one receiver (Rx) antenna, and at least one signalprocessor; and a graphical user interface (GUI); wherein the at leastone Tx antenna and the at least one Rx antenna are fixed in across-polarized orientation to each other; wherein the at least one Txantenna and the at least one Rx antenna are substantially perpendicularto a direction of travel of the at least one towing vessel, therebyreducing surface reflections in the at least one return signal; whereinthe at least one signal generator is operable to emit at least onetransmission signal to the target area through the at least one Txantenna, wherein the at least one transmission signal is an extremelylow frequency (ELF) signal; wherein the at least one transmission signalis a continuous-wave signal; wherein the at least one Rx antenna isoperable to receive at least one return signal from the target area,wherein the at least one return signal is based on the at least onetransmission signal; wherein the at least one signal processor isoperable to analyze amplitude data and phase shift data of the at leastone return signal; wherein the at least one signal processor is operableto detect a plurality of target objects in the target area based on theat least one return signal, and wherein the plurality of target objectsincludes ferrous and/or non-ferrous metals; wherein the GUI is operableto map and display the plurality of target objects in the target area;and wherein the underwater environments are saltwater environments. 2.The system of claim 1, wherein the at least one towing vessel includes afloatation device, and wherein the antenna system is connected to thefloatation device.
 3. The system of claim 1, wherein the antenna systemincludes a plurality of Rx antennas for each of the at least one Txantennas.
 4. The system of claim 1, wherein the at least one signalgenerator is operable to generate a plurality of transmission signals,and wherein the plurality of transmission signals have differentfrequencies.
 5. The system of claim 1, wherein the at least one signalprocessor is operable to identify constructive interference zones anddestructive interference zones in the target area based on the antennasystem and the at least one transmission signal.
 6. The system of claim1, wherein the at least one signal processor uses a baseline signal tonormalize the at least one return signal.
 7. The system of claim 1,wherein the antenna system is operable to adjust transmission powerlevels of at least one additional transmission signal emitted to thetarget area and/or return power levels of at least one additional returnsignal from the target area after receiving the at least one returnsignal.
 8. The system of claim 1, wherein the at least one signalprocessor is operable to distinguish between different metals composingthe plurality of target objects based on conductivity and wherein the atleast one signal processor is operable to determine a size of a targetobject based on at least two return signals, wherein each of the atleast two return signals has a different frequency.
 9. The system ofclaim 1, wherein the at least one signal processor is operable to detectand identify the plurality of target objects in real time or near realtime.
 10. A radar system for detecting ferrous and non-ferrous metals inunderwater environments, comprising: at least one towing vesselconfigured to traverse a target area; an antenna system including atleast one signal generator, at least one transmitter (Tx) antenna, atleast one receiver (Rx) antenna, and at least one signal processor;wherein the at least one Tx antenna and the at least one Rx antenna arefixed in a cross-polarized orientation to each other; wherein the atleast one Tx antenna and the at least one Rx antenna are substantiallyperpendicular to a direction of travel of the at least one towingvessel, thereby reducing surface reflections in the at least one returnsignal; a geolocation system; and a graphical user interface (GUI);wherein the at least one signal generator is operable to emit at leastone transmission signal to the target area through the at least one Txantenna, wherein the at least one transmission signal is an extremelylow frequency (ELF) signal; wherein the at least one transmission signalis a continuous-wave signal; wherein the at least one Rx antenna isoperable to receive at least one return signal from the target area,wherein the at least one return signal is based on the at least onetransmission signal; wherein the at least one signal processor isoperable to analyze amplitude data and phase shift data of the at leastone return signal; wherein the at least one signal processor is operableto detect a plurality of target objects in the target area based on theat least one return signal, and wherein the plurality of target objectsincludes ferrous and/or non-ferrous metals; wherein the at least onesignal processor is operable to determine a relative geolocation and/oran absolute geolocation of the plurality of target objects based on theat least one return signal and the geolocation system; wherein the GUIis operable to map and display the plurality of target objects in thetarget area; and wherein the underwater environments are saltwaterenvironments.
 11. The system of claim 10, wherein the geolocation systemincludes a plurality of signal reflectors in the underwater environment,and wherein the relative geolocation of the plurality of target objectsis based on the plurality of signal reflectors.
 12. A method fordetecting ferrous and non-ferrous metals in underwater environments,comprising: at least one towing vessel traversing a target area in arepeating pattern; at least one signal generator emitting at least onetransmission signal to the target area through at least one transmitter(Tx) antenna; at least one receiver (Rx) antenna receiving at least onereturn signal from the target area; wherein the at least one Tx antennaand the at least one Rx antenna are fixed in a cross-polarizedorientation to each other; wherein the at least one Tx antenna and theat least one Rx antenna are substantially perpendicular to a directionof travel of the at least one towing vessel, thereby reducing surfacereflections in the at least one return signal; the at least one signalprocessor analyzing amplitude data and phase shift data of the at leastone return signal; at least one signal processor processing the at leastone return signal to detect a plurality of target objects in the targetarea; and a graphical user interface (GUI) mapping and displaying theplurality of target objects in the target area; wherein the at least onetransmission signal is an extremely low frequency (ELF) signal; whereinthe at least one transmission signal is a continuous-wave signal;wherein the plurality of target objects includes ferrous and/ornon-ferrous metals; and wherein the underwater environments aresaltwater environments.
 13. The method of claim 12, wherein the towingvessel traverses at least one portion of the target area multiple times.14. The method of claim 12, wherein the at least one signal generatoremitting at least one transmission signal to the target area through atleast one Tx antenna includes the at least one signal generator emittinga plurality of transmission signals, wherein the plurality oftransmission signals have different frequencies.
 15. The method of claim12, further comprising the at least one signal generator adjustingtransmission power levels of at least one additional transmission signalemitted to the target area and/or return power levels of at least oneadditional return signal from the target area after receiving the atleast one return signal.
 16. The method of claim 12, further comprisingthe at least one signal processor identifying constructive interferencezones and destructive interference zones in the target area based on theat least one transmission signal, the at least one Tx antenna, and theat least one Rx antenna.
 17. The method of claim 12, wherein the atleast one signal processor processing the at least one return signal todetect a plurality of target objects in the target area includes the atleast one signal processor distinguishing between different metalscomposing the plurality of target objects based on conductivity and theat least one signal processor determining a size of the point targetbased on at least two return signals, wherein each of the at least tworeturn signals has a different frequency.
 18. The system of claim 1,wherein the at least one signal processor is operable to determine asize, a shape, and/or an orientation of the plurality of target objects.19. The system of claim 10, wherein the geolocation system includes afirst geolocation unit and a second geolocation unit and wherein thefirst geolocation unit is located on a floatation device, wherein thefloatation device is connected to the at least one towing vessel with atow cable, and wherein the geolocation system is operable to determine abaseline for the first geolocation unit and the second geolocation unit.20. The system of claim 10, wherein the at least one signal generator isoperable to generate a plurality of transmission signals, and whereinthe plurality of transmission signals have different frequencies.